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1292. Maximum Side Length of a Square with Sum Less than or Equal to Threshold 👍

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class Solution {
 public:
  int maxSideLength(vector<vector<int>>& mat, int threshold) {
    const int m = mat.size();
    const int n = mat[0].size();
    int ans = 0;
    vector<vector<int>> prefix(m + 1, vector<int>(n + 1));

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        prefix[i + 1][j + 1] =
            mat[i][j] + prefix[i][j + 1] + prefix[i + 1][j] - prefix[i][j];

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        for (int length = ans; length < min(m - i, n - j); ++length) {
          if (squareSum(prefix, i, j, i + length, j + length) > threshold)
            break;
          ans = max(ans, length + 1);
        }

    return ans;
  }

 private:
  int squareSum(vector<vector<int>>& prefix, int r1, int c1, int r2, int c2) {
    return prefix[r2 + 1][c2 + 1] - prefix[r1][c2 + 1] - prefix[r2 + 1][c1] +
           prefix[r1][c1];
  }
};

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class Solution {
  public int maxSideLength(int[][] mat, int threshold) {
    final int m = mat.length;
    final int n = mat[0].length;
    int ans = 0;
    int[][] prefix = new int[m + 1][n + 1];

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        prefix[i + 1][j + 1] = mat[i][j] + prefix[i][j + 1] + prefix[i + 1][j] - prefix[i][j];

    for (int i = 0; i < m; ++i)
      for (int j = 0; j < n; ++j)
        for (int length = ans; length < Math.min(m - i, n - j); ++length) {
          if (squareSum(prefix, i, j, i + length, j + length) > threshold)
            break;
          ans = Math.max(ans, length + 1);
        }

    return ans;
  }

  private int squareSum(int[][] prefix, int r1, int c1, int r2, int c2) {
    return prefix[r2 + 1][c2 + 1] - prefix[r1][c2 + 1] - prefix[r2 + 1][c1] + prefix[r1][c1];
  }
}

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class Solution:
  def maxSideLength(self, mat: list[list[int]], threshold: int) -> int:
    m = len(mat)
    n = len(mat[0])
    ans = 0
    prefix = [[0] * (n + 1) for _ in range(m + 1)]

    for i in range(m):
      for j in range(n):
        prefix[i + 1][j + 1] = (mat[i][j] + prefix[i][j + 1] +
                                prefix[i + 1][j] - prefix[i][j])

    def squareSum(r1: int, c1: int, r2: int, c2: int) -> int:
      return prefix[r2 + 1][c2 + 1] - prefix[r1][c2 + 1] - prefix[r2 + 1][c1] + prefix[r1][c1]

    for i in range(m):
      for j in range(n):
        for length in range(ans, min(m - i, n - j)):
          if squareSum(i, j, i + length, j + length) > threshold:
            break
          ans = max(ans, length + 1)

    return ans