2026/04/25

[LeetCode] 48 Rotate Image

正面實作轉90度極度難寫XD

改用轉置+反轉row

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class Solution {
public:
  void rotate(vector<vector<int>>& matrix) {
    int N = matrix.size();

    // step 1 : transpose
    for (int i = 0; i < N; i++) {
      for (int j = i + 1; j < N; j++) {
        int tmp = matrix[i][j];
        matrix[i][j] = matrix[j][i];
        matrix[j][i] = tmp;
      }
    }

    // step 2 : reverse each row
    for (int i = 0; i < N; i++) {
      for (int j = 0; j < N / 2; j++) {
        int tmp = matrix[i][j];
        matrix[i][j] = matrix[i][N - j - 1];
        matrix[i][N - j - 1] = tmp;
      }
    }
  }
};
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