hdu_1845 Jimmy’s Assignment 二分图匹配

#include<cstdio>#include<cstring>#include<algorithm>#include<vector>using namespace std;#define N 5001vector<int> g[N];int linker[N];bool vis[N];bool dfs(int u){for(int i=0;i<g[u].size();i++){int v=g[u][i];if(!vis[v]){vis[v]=1;if(linker[v]==-1||dfs(linker[v])){linker[v]=u;return true;}}}return false;}int hungary(int n){int cnt=0;memset(linker,-1,sizeof(linker));for(int i=1;i<=n;i++){memset(vis,0,sizeof(vis));if(dfs(i)) cnt++;}return cnt;}int main(){int t,n;scanf("%d",&t);while(t--){scanf("%d",&n);for(int i=1;i<=n;i++){g[i].clear();}int num=3*n/2;int r,c;while(num--){scanf("%d%d",&r,&c);g[r].push_back(c);g[c].push_back(r);}printf("%d\n",hungary(n)/2);}return 0;}

居然没超时！

A matching is a subset of the graph’s edges, such that no two edges in the subset have a common vertex.

这句话就是说一个点只能连一条边。就是二分图匹配了。