题目链接:点击打开链接
网络流dinic模板
刘汝佳版
代码:
#include <iostream> #include <cstdio> #include <cstring> #include <vector> #include <queue> #define inf 10000000 #define maxn 1000 using namespace std; struct edge{ int from,to,cap,flow; edge(){} edge(int from,int to,int cap,int flow):from(from),to(to),cap(cap),flow(flow){} }; struct dinic{ int n,m,s,t; vector<edge> edges; vector<int > G[maxn]; bool vis[maxn]; int cur[maxn]; int d[maxn]; void addedge(int from,int to,int cap){ edges.push_back(edge(from,to,cap,0)); edges.push_back(edge(to,from,0,0)); m=edges.size(); G[from].push_back(m-2); G[to].push_back(m-1); } bool bfs(){ memset(vis,0,sizeof(vis)); queue <int> Q; Q.push(s); d[s]=0; vis[s]=1; while(!Q.empty()){ int x=Q.front(); Q.pop(); for(int i=0;i<G[x].size();i++){ edge &e=edges[G[x][i]]; if(!vis[e.to]&&e.cap>e.flow){ vis[e.to]=1; d[e.to]=d[x]+1; Q.push(e.to); } } } return vis[t]; } int dfs(int x,int a){ if(x==t||a==0) return a; int flow=0; int f; for(int &i=cur[x];i<G[x].size();i++){ edge &e=edges[G[x][i]]; if((d[e.to]==d[x]+1)&&(f=dfs(e.to,min(e.cap-e.flow,a)))>0){ e.flow+=f; edges[G[x][i]^1].flow-=f; flow+=f; a-=f; if(a==0) break; } } return flow; } int maxflow(int a,int b){ s=a;t=b; int flow=0; while(bfs()){ memset(cur,0,sizeof(cur)); flow+=dfs(s,inf); } return flow; } }; int main(){ int m,n; while(~scanf("%d%d",&m,&n)){ dinic D; for(int i=1;i<=m;i++){ int s,t,d; scanf("%d%d%d",&s,&t,&d); D.addedge(s,t,d); } int res=D.maxflow(1,n); printf("%d\n",res); } return 0; }