LightOJ 1403 - Air Raid【二分匹配】

题目链接：http://www.lightoj.com/volume_showproblem.php?problem=1403

代码：

#include <iostream>
#include <algorithm>
#include <set>
#include <map>
#include <string.h>
#include <queue>
#include <sstream>
#include <stdio.h>
#include <math.h>
#include <stdlib.h>  

using namespace std;

int n, m;
int p[1010][1010];
int book[1010];
int match[1010];
vector<int> g[1010];

int dfs(int u)
{
    int i;
    for (i = 0; i < g[u].size(); i++)
    {
        int v = g[u][i];
        if (book[v] == 0 && p[u][v] == 1)
        {
            book[v] = 1;
            if (match[v] == 0 || dfs(match[v]))
            {
                match[v] = u;
                return 1;
            }
        }
    }
    return 0;
}

int main()
{
    int t;
    int cases = 1;
    scanf("%d", &t);
    while (t--)
    {
        scanf("%d%d", &n, &m);
        for (int i = 0; i <= n; i++) g[i].clear();

        int ans = 0;
        memset(match, 0, sizeof(match));
        memset(p, 0, sizeof(p));

        int a, b;
        while (m--)
        {
            scanf("%d%d", &a, &b);
            p[a][b] = 1;
            g[a].push_back(b);
        }

        for (int i = 1; i <= n; i++)
        {
            memset(book, 0, sizeof(book));
            if (dfs(i))
                ans++;
        }
        printf("Case %d: %d\n", cases++, n - ans);
    }
    return 0;
}

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