HDU1845Jimmy’s Assignment（无向图，最大匹配）

题意：就是求最大匹配

#include<cstdio>#include<iostream>#include<algorithm>#include<cmath>#include<set>#include<map>#include<string>#include<cstring>#include<stack>#include<queue>#include<vector>#include<limits>#include<ctime>#include<cassert>#include<cstdlib>#define lson (rt<<1),L,M#define rson (rt<<1|1),M+1,R#define M ((L+R)>>1)#define cl(a,b) memset(a,b,sizeof(a));#define LL long long#define P pair<int,int>#define X first#define Y second#define pb push_back#define fread(a) freopen(a,"r",stdin);#define fwrite(a) freopen(a,"w",stdout);using namespace std;const int maxn=5005;const int inf=999999;vector<int> G[maxn];int matching[maxn];bool vis[maxn];int num;bool dfs(int u){    int N=G[u].size();    for(int i=0;i<N;i++){        int v=G[u][i];        if(vis[v])continue;        vis[v]=true;        if(matching[v]==-1||dfs(matching[v])){            matching[v]=u;            return true;        }    }    return false;}int hungar(){    int ans=0;    cl(matching,-1);    for(int i=0;i<num;i++){        cl(vis,false);        if(dfs(i))ans++;    }    return ans/2;//无向边，算了全部，除2}int main(){    int T;    scanf("%d",&T);    while(T--){        int n;        scanf("%d",&n);        for(int i=0;i<=n;i++)G[i].clear();        int m=n*3/2;        while(m--){            int x,y;            scanf("%d%d",&x,&y);            x--;y--;            G[x].pb(y);//这里是无向边            G[y].pb(x);        }        num=n;        int ans=hungar();        printf("%d\n",ans);    }    return 0;}