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class Solution {
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  public List<Integer> spiralOrder(int[][] matrix) {
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    List<Integer> ans = new ArrayList<>();
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    int top = 0, left = 0, bottom = matrix.length - 1, right = matrix[0].length - 1;
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    while (top <= bottom && left <= right) {
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      for (int i = left; i <= right; i++) ans.add(matrix[top][i]);
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      top++;
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      for (int i = top; i <= bottom; i++) ans.add(matrix[i][right]);
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      right--;
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      if (top <= bottom) {
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        for (int i = right; i >= left; i--) ans.add(matrix[bottom][i]);
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        bottom--;
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      }
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      if (left <= right) {
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        for (int i = bottom; i >= top; i--) ans.add(matrix[i][left]);
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        left++;
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      }
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    }
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    return ans;
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  }
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}