标签：log coder bfs scan map .net ++ flow math
http://hihocoder.com/problemset/problem/1369?sid=1328132
参考 https://blog.csdn.net/a1799342217/article/details/73195243
https://blog.csdn.net/a519781181/article/details/51908303
【AC1】
#include<iostream> #include<cstdio> #include<cstring> #include<string> #include<cmath> #include<algorithm> #include<queue> #include<map> using namespace std; typedef long long ll; int n,m; const int maxn=5e2+2; const int maxm=2e4+2; const int inf=0x3f3f3f3f; int maxflow; struct edge{ int to; int nxt; int w; }e[2*maxm]; int head[maxn]; int tot; int fa[maxn]; int mp[maxn][maxn]; bool vis[maxn]; void init(){ memset(mp,-1,sizeof(mp)); memset(head,-1,sizeof(head)); tot=0; maxflow=0; } void add(int u,int v){ e[tot].to=v; e[tot].nxt=head[u]; head[u]=tot++; } bool bfs(int s,int t){ memset(vis,false,sizeof(vis)); memset(fa,-1,sizeof(fa)); queue<int> Q; Q.push(s); while(!Q.empty()){ int u=Q.front(); Q.pop(); if(u==t) return true; if(vis[u]) continue; vis[u]=true; for(int i=head[u];i!=-1;i=e[i].nxt){ int v=e[i].to; if(!vis[v]&&mp[u][v]){ fa[v]=u; Q.push(v); } } } return false; } int max_flow(int s,int t){ int flow=0; // int cnt=0; while(bfs(s,t)){ // for(int i=1;i<=n;i++){ // for(int j=1;j<=n;j++){ // cout<<mp[i][j]<<" "; // } // cout<<endl; // } // cout<<"**********************"<<endl; // cnt++; int u=t; int delta=inf; while(fa[u]!=-1){ // cout<<u<<" "; delta=min(delta,mp[fa[u]][u]); u=fa[u]; } // cout<<endl; // cout<<delta<<endl; flow+=delta; u=t; while(fa[u]!=-1){ mp[fa[u]][u]-=delta; mp[u][fa[u]]+=delta; u=fa[u]; } } return flow; } int main(){ while(~scanf("%d%d",&n,&m)){ init(); int u,v,c; for(int i=1;i<=m;i++){ scanf("%d%d%d",&u,&v,&c); if(mp[u][v]==-1){ add(u,v); add(v,u); mp[u][v]=c; mp[v][u]=0; }else{ mp[u][v]+=c; } } int ans=max_flow(1,n); printf("%d\n",ans); } return 0; }
【AC2】
#include<iostream> #include<cstdio> #include<cstring> #include<string> #include<cmath> #include<algorithm> #include<queue> #include<map> using namespace std; typedef long long ll; int n,m; const int maxn=5e2+2; const int maxm=2e4+2; const int inf=0x3f3f3f3f; struct edge{ int to; int nxt; int w; }e[maxm<<1]; int head[maxn]; struct node{ int x; int e; }fa[maxn]; bool vis[maxn]; int tot; void init(){ memset(head,-1,sizeof(head)); tot=0; } void add(int u,int v,int c){ e[tot].to=v; e[tot].w=c; e[tot].nxt=head[u]; head[u]=tot++; } bool bfs(int s,int t){ memset(vis,false,sizeof(vis)); queue<int> Q; Q.push(s); vis[s]=true; while(!Q.empty()){ int u=Q.front(); Q.pop(); if(u==t) return true; for(int i=head[u];i!=-1;i=e[i].nxt){ int v=e[i].to; int w=e[i].w; if(!vis[v]&&w){ Q.push(v); vis[v]=true; fa[v].x=u; fa[v].e=i; } } } return false; } int work(){ int s=1,t=n; for(int i=1;i<=n;i++){ fa[i].e=-1; fa[i].x=-1; } int ans=0; while(bfs(s,t)){ int delta=inf; int u=t; while(fa[u].x!=-1){ delta=min(delta,e[fa[u].e].w); u=fa[u].x; } ans+=delta; u=t; while(fa[u].x!=-1){ int i=fa[u].e; e[i].w-=delta; e[i^1].w+=delta; u=fa[u].x; } for(int i=1;i<=n;i++){ fa[i].e=-1; fa[i].x=-1; } } return ans; } int main(){ while(~scanf("%d%d",&n,&m)){ init(); int u,v,c; for(int i=1;i<=m;i++){ scanf("%d%d%d",&u,&v,&c); add(u,v,c); add(v,u,0); } int ans=work(); printf("%d\n",ans); } return 0; }
【最大流】hihocoder 1369 : 网络流一·Ford-Fulkerson算法
标签：log coder bfs scan map .net ++ flow math
原文地址：https://www.cnblogs.com/itcsl/p/9200994.html
