{
  "generatedAt": "2026-11-10T01:03:37.197Z",
  "generator": "scripts/review.mjs",
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    {
      "id": "P1",
      "title": "Longest substring without repeating characters",
      "statement": "Given a string s, return the length of the longest substring without repeating characters. Constraints: 0 <= s.length <= 5 * 10^4.",
      "visibleCount": 3,
      "hiddenCount": 4,
      "hiddenClasses": [
        "empty-input",
        "whitespace",
        "pointer-jump",
        "stale-index"
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    },
    {
      "id": "P2",
      "title": "Valid parentheses",
      "statement": "Given a string s containing just ()[]{}, determine if the input string is valid. Constraints: 1 <= s.length <= 10^4.",
      "visibleCount": 3,
      "hiddenCount": 3,
      "hiddenClasses": [
        "unmatched-open",
        "pop-empty",
        "interleaved"
      ]
    },
    {
      "id": "P3",
      "title": "Merge two sorted lists",
      "statement": "Merge two sorted linked lists and return it as a sorted list.",
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      "hiddenCount": 2,
      "hiddenClasses": [
        "first-list-bias",
        "duplicate-drop"
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    }
  ],
  "matrix": [
    {
      "problemId": "P1",
      "candidateId": "ref",
      "label": "Reference",
      "role": "reference",
      "visiblePass": true,
      "hiddenPass": true,
      "verdict": "correct",
      "visible": [
        {
          "case": {
            "input": "abcabcbb",
            "expected": 3
          },
          "result": {
            "status": "pass",
            "actual": 3
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        {
          "case": {
            "input": "bbbbb",
            "expected": 1
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          "result": {
            "status": "pass",
            "actual": 1
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        {
          "case": {
            "input": "pwwkew",
            "expected": 3
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          "result": {
            "status": "pass",
            "actual": 3
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      ],
      "hidden": [
        {
          "case": {
            "input": "",
            "expected": 0,
            "catches": "Solutions that assume s.length >= 1.",
            "class": "empty-input"
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          "result": {
            "status": "pass",
            "actual": 0
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        {
          "case": {
            "input": " ",
            "expected": 1,
            "catches": "Solutions that strip whitespace.",
            "class": "whitespace"
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            "status": "pass",
            "actual": 1
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        },
        {
          "case": {
            "input": "dvdf",
            "expected": 3,
            "catches": "Solutions that jump left to i.",
            "class": "pointer-jump"
          },
          "result": {
            "status": "pass",
            "actual": 3
          }
        },
        {
          "case": {
            "input": "abba",
            "expected": 2,
            "catches": "Solutions that move left backwards.",
            "class": "stale-index"
          },
          "result": {
            "status": "pass",
            "actual": 2
          }
        }
      ],
      "firstHiddenFailure": null,
      "note": "Passes the visible tests and every hidden case derived from the stated constraints."
    },
    {
      "problemId": "P1",
      "candidateId": "A",
      "label": "A — left can move backwards",
      "role": "edge-case-candidate",
      "visiblePass": true,
      "hiddenPass": false,
      "verdict": "edge-case-broken",
      "visible": [
        {
          "case": {
            "input": "abcabcbb",
            "expected": 3
          },
          "result": {
            "status": "pass",
            "actual": 3
          }
        },
        {
          "case": {
            "input": "bbbbb",
            "expected": 1
          },
          "result": {
            "status": "pass",
            "actual": 1
          }
        },
        {
          "case": {
            "input": "pwwkew",
            "expected": 3
          },
          "result": {
            "status": "pass",
            "actual": 3
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": "",
            "expected": 0,
            "catches": "Solutions that assume s.length >= 1.",
            "class": "empty-input"
          },
          "result": {
            "status": "pass",
            "actual": 0
          }
        },
        {
          "case": {
            "input": " ",
            "expected": 1,
            "catches": "Solutions that strip whitespace.",
            "class": "whitespace"
          },
          "result": {
            "status": "pass",
            "actual": 1
          }
        },
        {
          "case": {
            "input": "dvdf",
            "expected": 3,
            "catches": "Solutions that jump left to i.",
            "class": "pointer-jump"
          },
          "result": {
            "status": "pass",
            "actual": 3
          }
        },
        {
          "case": {
            "input": "abba",
            "expected": 2,
            "catches": "Solutions that move left backwards.",
            "class": "stale-index"
          },
          "result": {
            "status": "fail",
            "actual": 3,
            "expected": 2
          }
        }
      ],
      "firstHiddenFailure": {
        "input": "abba",
        "expected": 2,
        "actual": 3,
        "error": null,
        "catches": "Solutions that move left backwards.",
        "class": "stale-index"
      },
      "note": "Passes every visible test and fails on input \"abba\" (expected 2, got 3). Solutions that move left backwards."
    },
    {
      "problemId": "P1",
      "candidateId": "A2",
      "label": "A2 — left jumps to i",
      "role": "edge-case-candidate",
      "visiblePass": true,
      "hiddenPass": false,
      "verdict": "edge-case-broken",
      "visible": [
        {
          "case": {
            "input": "abcabcbb",
            "expected": 3
          },
          "result": {
            "status": "pass",
            "actual": 3
          }
        },
        {
          "case": {
            "input": "bbbbb",
            "expected": 1
          },
          "result": {
            "status": "pass",
            "actual": 1
          }
        },
        {
          "case": {
            "input": "pwwkew",
            "expected": 3
          },
          "result": {
            "status": "pass",
            "actual": 3
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": "",
            "expected": 0,
            "catches": "Solutions that assume s.length >= 1.",
            "class": "empty-input"
          },
          "result": {
            "status": "pass",
            "actual": 0
          }
        },
        {
          "case": {
            "input": " ",
            "expected": 1,
            "catches": "Solutions that strip whitespace.",
            "class": "whitespace"
          },
          "result": {
            "status": "pass",
            "actual": 1
          }
        },
        {
          "case": {
            "input": "dvdf",
            "expected": 3,
            "catches": "Solutions that jump left to i.",
            "class": "pointer-jump"
          },
          "result": {
            "status": "fail",
            "actual": 2,
            "expected": 3
          }
        },
        {
          "case": {
            "input": "abba",
            "expected": 2,
            "catches": "Solutions that move left backwards.",
            "class": "stale-index"
          },
          "result": {
            "status": "pass",
            "actual": 2
          }
        }
      ],
      "firstHiddenFailure": {
        "input": "dvdf",
        "expected": 3,
        "actual": 2,
        "error": null,
        "catches": "Solutions that jump left to i.",
        "class": "pointer-jump"
      },
      "note": "Passes every visible test and fails on input \"dvdf\" (expected 3, got 2). Solutions that jump left to i."
    },
    {
      "problemId": "P1",
      "candidateId": "B",
      "label": "B — off-by-one",
      "role": "incorrect-candidate",
      "visiblePass": false,
      "hiddenPass": false,
      "verdict": "incorrect",
      "visible": [
        {
          "case": {
            "input": "abcabcbb",
            "expected": 3
          },
          "result": {
            "status": "fail",
            "actual": 2,
            "expected": 3
          }
        },
        {
          "case": {
            "input": "bbbbb",
            "expected": 1
          },
          "result": {
            "status": "fail",
            "actual": 0,
            "expected": 1
          }
        },
        {
          "case": {
            "input": "pwwkew",
            "expected": 3
          },
          "result": {
            "status": "fail",
            "actual": 2,
            "expected": 3
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": "",
            "expected": 0,
            "catches": "Solutions that assume s.length >= 1.",
            "class": "empty-input"
          },
          "result": {
            "status": "pass",
            "actual": 0
          }
        },
        {
          "case": {
            "input": " ",
            "expected": 1,
            "catches": "Solutions that strip whitespace.",
            "class": "whitespace"
          },
          "result": {
            "status": "fail",
            "actual": 0,
            "expected": 1
          }
        },
        {
          "case": {
            "input": "dvdf",
            "expected": 3,
            "catches": "Solutions that jump left to i.",
            "class": "pointer-jump"
          },
          "result": {
            "status": "fail",
            "actual": 2,
            "expected": 3
          }
        },
        {
          "case": {
            "input": "abba",
            "expected": 2,
            "catches": "Solutions that move left backwards.",
            "class": "stale-index"
          },
          "result": {
            "status": "fail",
            "actual": 1,
            "expected": 2
          }
        }
      ],
      "firstHiddenFailure": {
        "input": " ",
        "expected": 1,
        "actual": 0,
        "error": null,
        "catches": "Solutions that strip whitespace.",
        "class": "whitespace"
      },
      "note": "Fails at least one visible test. Wrong answer on a case the candidate was shown."
    },
    {
      "problemId": "P2",
      "candidateId": "ref",
      "label": "Reference",
      "role": "reference",
      "visiblePass": true,
      "hiddenPass": true,
      "verdict": "correct",
      "visible": [
        {
          "case": {
            "input": "()",
            "expected": true
          },
          "result": {
            "status": "pass",
            "actual": true
          }
        },
        {
          "case": {
            "input": "()[]{}",
            "expected": true
          },
          "result": {
            "status": "pass",
            "actual": true
          }
        },
        {
          "case": {
            "input": "(]",
            "expected": false
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": "(",
            "expected": false,
            "catches": "No bracket match check.",
            "class": "unmatched-open"
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        },
        {
          "case": {
            "input": "]",
            "expected": false,
            "catches": "Pop from empty stack.",
            "class": "pop-empty"
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        },
        {
          "case": {
            "input": "([)]",
            "expected": false,
            "catches": "Counting instead of matching.",
            "class": "interleaved"
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        }
      ],
      "firstHiddenFailure": null,
      "note": "Passes the visible tests and every hidden case derived from the stated constraints."
    },
    {
      "problemId": "P2",
      "candidateId": "A",
      "label": "A — counts brackets",
      "role": "edge-case-candidate",
      "visiblePass": true,
      "hiddenPass": false,
      "verdict": "edge-case-broken",
      "visible": [
        {
          "case": {
            "input": "()",
            "expected": true
          },
          "result": {
            "status": "pass",
            "actual": true
          }
        },
        {
          "case": {
            "input": "()[]{}",
            "expected": true
          },
          "result": {
            "status": "pass",
            "actual": true
          }
        },
        {
          "case": {
            "input": "(]",
            "expected": false
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": "(",
            "expected": false,
            "catches": "No bracket match check.",
            "class": "unmatched-open"
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        },
        {
          "case": {
            "input": "]",
            "expected": false,
            "catches": "Pop from empty stack.",
            "class": "pop-empty"
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        },
        {
          "case": {
            "input": "([)]",
            "expected": false,
            "catches": "Counting instead of matching.",
            "class": "interleaved"
          },
          "result": {
            "status": "fail",
            "actual": true,
            "expected": false
          }
        }
      ],
      "firstHiddenFailure": {
        "input": "([)]",
        "expected": false,
        "actual": true,
        "error": null,
        "catches": "Counting instead of matching.",
        "class": "interleaved"
      },
      "note": "Passes every visible test and fails on input \"([)]\" (expected false, got true). Counting instead of matching."
    },
    {
      "problemId": "P2",
      "candidateId": "B",
      "label": "B — no match check",
      "role": "incorrect-candidate",
      "visiblePass": false,
      "hiddenPass": false,
      "verdict": "incorrect",
      "visible": [
        {
          "case": {
            "input": "()",
            "expected": true
          },
          "result": {
            "status": "pass",
            "actual": true
          }
        },
        {
          "case": {
            "input": "()[]{}",
            "expected": true
          },
          "result": {
            "status": "pass",
            "actual": true
          }
        },
        {
          "case": {
            "input": "(]",
            "expected": false
          },
          "result": {
            "status": "fail",
            "actual": true,
            "expected": false
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": "(",
            "expected": false,
            "catches": "No bracket match check.",
            "class": "unmatched-open"
          },
          "result": {
            "status": "pass",
            "actual": false
          }
        },
        {
          "case": {
            "input": "]",
            "expected": false,
            "catches": "Pop from empty stack.",
            "class": "pop-empty"
          },
          "result": {
            "status": "fail",
            "actual": true,
            "expected": false
          }
        },
        {
          "case": {
            "input": "([)]",
            "expected": false,
            "catches": "Counting instead of matching.",
            "class": "interleaved"
          },
          "result": {
            "status": "fail",
            "actual": true,
            "expected": false
          }
        }
      ],
      "firstHiddenFailure": {
        "input": "]",
        "expected": false,
        "actual": true,
        "error": null,
        "catches": "Pop from empty stack.",
        "class": "pop-empty"
      },
      "note": "Fails at least one visible test. Wrong answer on a case the candidate was shown."
    },
    {
      "problemId": "P3",
      "candidateId": "ref",
      "label": "Reference",
      "role": "reference",
      "visiblePass": true,
      "hiddenPass": true,
      "verdict": "correct",
      "visible": [
        {
          "case": {
            "input": [
              [
                1,
                2,
                4
              ],
              [
                1,
                3,
                4
              ]
            ],
            "expected": [
              1,
              1,
              2,
              3,
              4,
              4
            ]
          },
          "result": {
            "status": "pass",
            "actual": [
              1,
              1,
              2,
              3,
              4,
              4
            ]
          }
        },
        {
          "case": {
            "input": [
              [],
              []
            ],
            "expected": []
          },
          "result": {
            "status": "pass",
            "actual": []
          }
        },
        {
          "case": {
            "input": [
              [],
              [
                0
              ]
            ],
            "expected": [
              0
            ]
          },
          "result": {
            "status": "pass",
            "actual": [
              0
            ]
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": [
              [
                5
              ],
              [
                1,
                2,
                3
              ]
            ],
            "expected": [
              1,
              2,
              3,
              5
            ],
            "catches": "First-list bias.",
            "class": "first-list-bias"
          },
          "result": {
            "status": "pass",
            "actual": [
              1,
              2,
              3,
              5
            ]
          }
        },
        {
          "case": {
            "input": [
              [
                1,
                1,
                1
              ],
              [
                1,
                1
              ]
            ],
            "expected": [
              1,
              1,
              1,
              1,
              1
            ],
            "catches": "Uses < not <=.",
            "class": "duplicate-drop"
          },
          "result": {
            "status": "pass",
            "actual": [
              1,
              1,
              1,
              1,
              1
            ]
          }
        }
      ],
      "firstHiddenFailure": null,
      "note": "Passes the visible tests and every hidden case derived from the stated constraints."
    },
    {
      "problemId": "P3",
      "candidateId": "A",
      "label": "A — always starts with first list",
      "role": "edge-case-candidate",
      "visiblePass": true,
      "hiddenPass": false,
      "verdict": "edge-case-broken",
      "visible": [
        {
          "case": {
            "input": [
              [
                1,
                2,
                4
              ],
              [
                1,
                3,
                4
              ]
            ],
            "expected": [
              1,
              1,
              2,
              3,
              4,
              4
            ]
          },
          "result": {
            "status": "pass",
            "actual": [
              1,
              1,
              2,
              3,
              4,
              4
            ]
          }
        },
        {
          "case": {
            "input": [
              [],
              []
            ],
            "expected": []
          },
          "result": {
            "status": "pass",
            "actual": []
          }
        },
        {
          "case": {
            "input": [
              [],
              [
                0
              ]
            ],
            "expected": [
              0
            ]
          },
          "result": {
            "status": "pass",
            "actual": [
              0
            ]
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": [
              [
                5
              ],
              [
                1,
                2,
                3
              ]
            ],
            "expected": [
              1,
              2,
              3,
              5
            ],
            "catches": "First-list bias.",
            "class": "first-list-bias"
          },
          "result": {
            "status": "fail",
            "actual": [
              5,
              1,
              2,
              3
            ],
            "expected": [
              1,
              2,
              3,
              5
            ]
          }
        },
        {
          "case": {
            "input": [
              [
                1,
                1,
                1
              ],
              [
                1,
                1
              ]
            ],
            "expected": [
              1,
              1,
              1,
              1,
              1
            ],
            "catches": "Uses < not <=.",
            "class": "duplicate-drop"
          },
          "result": {
            "status": "pass",
            "actual": [
              1,
              1,
              1,
              1,
              1
            ]
          }
        }
      ],
      "firstHiddenFailure": {
        "input": [
          [
            5
          ],
          [
            1,
            2,
            3
          ]
        ],
        "expected": [
          1,
          2,
          3,
          5
        ],
        "actual": [
          5,
          1,
          2,
          3
        ],
        "error": null,
        "catches": "First-list bias.",
        "class": "first-list-bias"
      },
      "note": "Passes every visible test and fails on input [[5],[1,2,3]] (expected [1,2,3,5], got [5,1,2,3]). First-list bias."
    },
    {
      "problemId": "P3",
      "candidateId": "B",
      "label": "B — reversed merge",
      "role": "incorrect-candidate",
      "visiblePass": false,
      "hiddenPass": false,
      "verdict": "incorrect",
      "visible": [
        {
          "case": {
            "input": [
              [
                1,
                2,
                4
              ],
              [
                1,
                3,
                4
              ]
            ],
            "expected": [
              1,
              1,
              2,
              3,
              4,
              4
            ]
          },
          "result": {
            "status": "fail",
            "actual": [
              1,
              3,
              4,
              1,
              2,
              4
            ],
            "expected": [
              1,
              1,
              2,
              3,
              4,
              4
            ]
          }
        },
        {
          "case": {
            "input": [
              [],
              []
            ],
            "expected": []
          },
          "result": {
            "status": "pass",
            "actual": []
          }
        },
        {
          "case": {
            "input": [
              [],
              [
                0
              ]
            ],
            "expected": [
              0
            ]
          },
          "result": {
            "status": "pass",
            "actual": [
              0
            ]
          }
        }
      ],
      "hidden": [
        {
          "case": {
            "input": [
              [
                5
              ],
              [
                1,
                2,
                3
              ]
            ],
            "expected": [
              1,
              2,
              3,
              5
            ],
            "catches": "First-list bias.",
            "class": "first-list-bias"
          },
          "result": {
            "status": "fail",
            "actual": [
              5,
              1,
              2,
              3
            ],
            "expected": [
              1,
              2,
              3,
              5
            ]
          }
        },
        {
          "case": {
            "input": [
              [
                1,
                1,
                1
              ],
              [
                1,
                1
              ]
            ],
            "expected": [
              1,
              1,
              1,
              1,
              1
            ],
            "catches": "Uses < not <=.",
            "class": "duplicate-drop"
          },
          "result": {
            "status": "pass",
            "actual": [
              1,
              1,
              1,
              1,
              1
            ]
          }
        }
      ],
      "firstHiddenFailure": {
        "input": [
          [
            5
          ],
          [
            1,
            2,
            3
          ]
        ],
        "expected": [
          1,
          2,
          3,
          5
        ],
        "actual": [
          5,
          1,
          2,
          3
        ],
        "error": null,
        "catches": "First-list bias.",
        "class": "first-list-bias"
      },
      "note": "Fails at least one visible test. Wrong answer on a case the candidate was shown."
    }
  ],
  "expectations": [
    {
      "problemId": "P1",
      "candidateId": "ref",
      "declaredRole": "reference",
      "actual": "correct",
      "agree": true
    },
    {
      "problemId": "P1",
      "candidateId": "A",
      "declaredRole": "edge-case-candidate",
      "actual": "edge-case-broken",
      "agree": true
    },
    {
      "problemId": "P1",
      "candidateId": "A2",
      "declaredRole": "edge-case-candidate",
      "actual": "edge-case-broken",
      "agree": true
    },
    {
      "problemId": "P1",
      "candidateId": "B",
      "declaredRole": "incorrect-candidate",
      "actual": "incorrect",
      "agree": true
    },
    {
      "problemId": "P2",
      "candidateId": "ref",
      "declaredRole": "reference",
      "actual": "correct",
      "agree": true
    },
    {
      "problemId": "P2",
      "candidateId": "A",
      "declaredRole": "edge-case-candidate",
      "actual": "edge-case-broken",
      "agree": true
    },
    {
      "problemId": "P2",
      "candidateId": "B",
      "declaredRole": "incorrect-candidate",
      "actual": "incorrect",
      "agree": true
    },
    {
      "problemId": "P3",
      "candidateId": "ref",
      "declaredRole": "reference",
      "actual": "correct",
      "agree": true
    },
    {
      "problemId": "P3",
      "candidateId": "A",
      "declaredRole": "edge-case-candidate",
      "actual": "edge-case-broken",
      "agree": true
    },
    {
      "problemId": "P3",
      "candidateId": "B",
      "declaredRole": "incorrect-candidate",
      "actual": "incorrect",
      "agree": true
    }
  ],
  "summary": {
    "total": 10,
    "correct": 3,
    "edgeCaseBroken": 4,
    "incorrect": 3,
    "threw": 0,
    "edgeCaseBrokenCandidates": [
      "P1/A",
      "P1/A2",
      "P2/A",
      "P3/A"
    ],
    "disagreements": 0,
    "sound": true
  }
}