// 1292. Maximum Side Length of a Square with Sum Less than or Equal to // Threshold #include "leetcode.h" /* * given a 'm x n' matrix 'mat' and an integer 'threshold', return the maximum * side-length of a square with a sum less than or equal to 'threshold' or * return 0 if there is no such square. */ int maxSideLength(int **mat, int matSize, int *matColSize, int threshold) { int w = matSize, h = matColSize[0], prefix[w][h]; for (int x = 0; x < w; x++) for (int y = 0; y < h; y++) prefix[x][y] = mat[x][y] + (x ? prefix[x - 1][y] : 0) + (y ? prefix[x][y - 1] : 0) - (x && y ? prefix[x - 1][y - 1] : 0); int max = w > h ? w : h, best = -1; for (int s = 0; s < max; s++) { for (int x = 0; x < w - s; x++) { for (int y = 0; y < h - s; y++) { int sum = prefix[x + s][y + s] - (x ? prefix[x - 1][y + s] : 0) - (y ? prefix[x + s][y - 1] : 0) + (x && y ? prefix[x - 1][y - 1] : 0); if (sum <= threshold) { best = s; break; } } if (best == s) break; } if (best != s) break; } return best + 1; } int main() { int m1i[3][7] = { {1, 1, 3, 2, 4, 3, 2}, {1, 1, 3, 2, 4, 3, 2}, {1, 1, 3, 2, 4, 3, 2}}; int m2i[4][5] = { {2, 2, 2, 2, 2}, {2, 2, 2, 2, 2}, {2, 2, 2, 2, 2}, {2, 2, 2, 2, 2}}; struct two_d_arr m1, m2; two_d_arr_init(&m1, 3, 7, m1i); two_d_arr_init(&m2, 4, 5, m2i); printf("%d\n", maxSideLength(m1.arr, m1.row_size, m1.col_size, 4)); // expect: 2 printf("%d\n", maxSideLength(m2.arr, m2.row_size, m2.col_size, 1)); // expect: 0 two_d_arr_free(&m1); two_d_arr_free(&m2); }