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class Solution {
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  public void swap(int[][] matrix, int n1, int m1, int n2, int m2) {
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    int a = matrix[n1][m1];
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    int temp = matrix[n2][m2];
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    matrix[n2][m2] = a;
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    matrix[n1][m1] = temp;
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  }
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  public void rotate(int[][] matrix) {
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    int n = matrix.length;
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    for (int i = 0; i < n / 2; i++) {
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      for (int j = 0; j < n; j++) {
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        swap(matrix, i, j, n - i - 1, j);
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      }
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    }
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    for (int i = n - 1; i >= 0; i--) {
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      for (int j = 0; j < i; j++) {
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        swap(matrix, i, j, j, i);
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      }
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    }
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  }
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}