1292

class Solution {
public:
    int maxSideLength(vector<vector<int>>& mat, int threshold) {
        int maxLen = 0;
        #define a(i, j) ((i<0 || j<0) ? 0: mat[i][j])
        int n = mat.size(), m = mat[0].size();

        for(int i=0; i<n; i++)
            for(int j=0; j<m; j++){
                mat[i][j] += a(i-1,j) + a(i,j-1) - a(i-1,j-1);
                maxLen += ((maxLen <= min(i, j)) && (a(i,j)-a(i-maxLen-1,j)-a(i,j-1-maxLen)+a(i-1-maxLen,j-1-maxLen) <= threshold));
            }
        return maxLen;
    }
};