Maximal Square LeetCode solution in Java

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class Solution {
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  public int maximalSquare(char[][] matrix) {
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    int m = matrix.length;
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    int n = matrix[0].length;
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    int[][] dp = new int[m][n];
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    int max = 0;
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    for (int i = 0; i < m; i++) {
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      dp[i][0] = matrix[i][0] - 48;
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      if (matrix[i][0] == '1') max = 1;
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    }
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    for (int i = 0; i < n; i++) {
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      dp[0][i] = matrix[0][i] - 48;
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      if (matrix[0][i] == '1') max = 1;
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    }
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    for (int i = 1; i < m; i++) {
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      for (int j = 1; j < n; j++) {
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        if (matrix[i][j] == '1') {
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          dp[i][j] = Math.min(dp[i - 1][j - 1], Math.min(dp[i][j - 1], dp[i - 1][j])) + 1;
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          if (dp[i][j] > max) {
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            max = dp[i][j];
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          }
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        }
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      }
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    }
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    return max * max;
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  }
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}