HDU 1151 Air Raid（最小路径覆盖）

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<iostream>
#include<vector>
#include<queue>
#include<cmath>
using namespace std;
#define INF 0x3fffffff
#define maxn 1705
int n, P[maxn],  Head[maxn], m, k;
bool vis[maxn];

struct EdgeNode
{
    int e, next;
}edge[maxn*5];

void AddEdge(int s, int e)
{
    edge[k].next = Head[s];
    edge[k].e = e;
    Head[s] = k ++;
}

void DFS2(int u)
{

}

bool Find(int u)
{
    for(int i=Head[u]; i!=-1; i=edge[i].next)
    {
        int v = edge[i].e;
        if(!vis[v] )
        {
            vis[v] = true;
            if(P[v] == -1 || Find(P[v]) )
            {
                P[v] = u;
                return true;
            }
        }
    }
    return false;
}

int solve()
{
    int ans = 0;
    memset(P, -1, sizeof(P));

    for(int i=1; i<=n; i++)
    {
        memset(vis, false, sizeof(vis));
        if( Find(i) )
            ans ++;
    }
    return n - ans;
}

int main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        scanf("%d %d",&n, &m);
        int a, b;
        k = 0;
        memset(Head, -1, sizeof(Head));
        for(int i=0; i<m; i++)
        {
            scanf("%d %d",&a, &b);
            AddEdge(a, b);
        }
        printf("%d\n", solve() );
    }
    return 0;
}