Largest Submatrix With Rearrangements LeetCode solution in Java

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class Solution {
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  public int largestSubmatrix(int[][] matrix) {
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    int m = matrix.length, n = matrix[0].length;
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    for (int i = 1; i < m; ++i) {
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      for (int j = 0; j < n; ++j) {
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        if (matrix[i][j] == 1) {
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          matrix[i][j] = matrix[i - 1][j] + 1;
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        }
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      }
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    }
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    int ans = 0;
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    for (var row : matrix) {
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      Arrays.sort(row);
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      for (int j = n - 1, k = 1; j >= 0 && row[j] > 0; --j, ++k) {
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        int s = row[j] * k;
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        ans = Math.max(ans, s);
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      }
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    }
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    return ans;
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  }
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}