UVa10502 - Counting Rectangles

#include <cstdio>
#include <cstring>

using namespace std;

const int N = 100;

short g[N][N];
bool check(int x1, int y1, int x2, int y2);

int main()
{
    int n, m;
    char ch;
    int x1, y1, x2, y2;
    int cnt;

#ifndef ONLINE_JUDGE
    freopen("uva_in.txt", "r", stdin);
#endif

    while (scanf("%d", &n) && n) {
        scanf("%d", &m);
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < m; ) {
                ch = getchar();
                    if (ch == '0' || ch == '1') {
                        g[i][j++] = ch - '0';
                    }
            }
        }
        
        cnt = 0;
        for (x1 = 0; x1 < n; x1++) {
            for ( y1 = 0; y1 < m; y1++) {
                for (x2 = x1; x2 < n; x2++) {
                    for (y2 = y1; y2 < m; y2++) {
                        if (check(x1, y1, x2, y2)) cnt++;        
                    }
                }
            }
        }

        printf("%d\n", cnt);
    }
    return 0;
}

bool check(int x1, int y1, int x2, int y2) 
{
    for (int i = x1; i <= x2; i++) {
        for (int j = y1; j <= y2; j++) {
            if (g[i][j] != 1) return false;
        }
    }

    return true;
}

上面用的是枚举法，效率不高，改成组合的计数方法，代码如下

#include <cstdio>
#include <algorithm>
#include <climits>

using namespace std;

#pragma warning(disable:4996)

const int N = 110;

int dp[N][N];
int row, col;
char buf[N];

bool input()
{
	scanf("%d", &row);
	if (row == 0) return false;

	scanf("%d", &col);
	for (int i = 1; i <= row; i++) {
		scanf("%s", buf);
		for (int j = 1; j <= col; j++) {
			if (buf[j - 1] == '1') dp[i][j] = 1;
			else dp[i][j] = 0;
		}
	}
	return true;
}



void solve()
{
	for (int i = 2; i <= row; i++) {
		for (int j = 1; j <= col; j++) {
			if (dp[i][j]) dp[i][j] += dp[i - 1][j];
		}
	}

	int ans = 0;
	for (int i = 1; i <= row; i++) {
		for(int j = 1; j <= col; j++) {
			int tmp = INT_MAX;
			for (int k = j; k <= col && dp[i][k]; k++) {
				tmp = min(tmp, dp[i][k]);
				ans += tmp;
			}
		}
	}

	printf("%d\n", ans);
}

int main()
{
#ifndef ONLINE_JUDGE
	freopen("f:\\OJ\\uva_in.txt", "r", stdin);
#endif

	while (input()) {
		solve();
	}

	return 0;
}