洛谷 P1387 最大正方形

用f[i][j]表示以（i,j）为右下角的最长正方形的边长
则 f[i][j] = min(f[i-1][j], min(f[i][j-1], f[i-1][j-1])) + 1;

#include<cstdio>
#include<algorithm>
#define REP(i, a, b) for(int i = (a); i < (b); i++)
#define _for(i, a, b) for(int i = (a); i <= (b); i++)
using namespace std;

const int MAXN = 112;
int f[MAXN][MAXN], ans, n, m;

int main()
{
	scanf("%d%d", &n, &m);
	_for(i, 1, n)
		_for(j, 1, m)
		{
			int x;
			scanf("%d", &x);
			if(x == 1) f[i][j] = min(f[i-1][j], min(f[i][j-1], f[i-1][j-1])) + 1;
			ans = max(ans, f[i][j]);
		}
	printf("%d\n", ans);
	return 0;
}