hdu2063 过山车（最大二分匹配）

强烈推荐的匈牙利算法介绍：http://www.renfei.org/blog/bipartite-matching.html

#include "iostream"
#include "vector"
#include "memory.h"
using namespace std;
#define swap(a,b,t) ( (t) = (x),(x) = (y),(y) = (t) )
#define MAXN 1010
int l[MAXN][MAXN];
bool flag[MAXN];
int re[MAXN];
int k,m,n;
int ans;

int find(int a)
{
    for (int i = 0;i <= n; ++ i) {
        if (l[a][i] == 1 && flag[i] == 0) {
            flag[i] = 1;
            if (re[i] == 0 || find(re[i])) {
                re[i] = a;
                return 1;
            }
        }
    }
    return 0;
}

void init()
{
    ans = 0;
    for (int i = 0;i <= m; ++ i)
        for (int j = 0;j <= n; ++ j)
            l[i][j] = 0;
    memset(re,0,sizeof(re));
}

int main()
{

    while (cin >> k,k) {
        init();
        ans = 0;
        cin >> m >> n;
        for (int i = 0; i < k; ++ i) {
            int a,b;
            cin >> a >> b;
            l[a][b] = 1;
        }
        for(int i = 1;i <= m; ++ i)    {
            memset(flag,0,sizeof(flag));
            if (find(i)) ans ++;
        }
        cout << ans << endl;
    }
    return 0;
}

欠一个BFS