题解 | 最大正方形周长动态规划求解

#include<stdio.h>

int min(int a, int b, int c) {
    if (a < b) return a < c ? a : c;
    else return b < c ? b : c;
}

int main() {
    int n, m;
    scanf("%d%d", &n, &m);
    int dp[n][m], matrix[n][m], max = 0;
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {
            scanf("%d", &matrix[i][j]);
            if (matrix[i][j] == 1) max = 1;
        }
    }
    for (int i = 0; i < n; i++) dp[i][0] = matrix[i][0];
    for (int j = 1; j < m; j++) dp[0][j] = matrix[0][j];
    for (int i = 1; i < n; i++) {
        for (int j = 1; j < m; j++) {
            if (matrix[i][j] == 1) {
                dp[i][j] = min(dp[i - 1][j], dp[i][j - 1], dp[i - 1][j - 1]) + 1;
                if (dp[i][j] > max) max = dp[i][j];
            } else dp[i][j] = 0;
        }
    }
    printf("%d\n", max * 4);
    return 0;
}