https://www.luogu.org/problemnew/show/P2740
题解：网络流+最大流
/* *@Author: STZG *@Language: C++ */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include //#define DEBUG #define RI register int #define endl "\n" using namespace std; typedef long long ll; //typedef __int128 lll; const int N=200+10; const int M=100000+10; const int MOD=1e9+7; const double PI = acos(-1.0); const double EXP = 1E-8; const int INF = 0x3f3f3f3f; int s,t,n,m,k,p,l,r,u,v,w,c2; int ans,cnt,flag,temp,sum; int dis[N]; struct node{ int u,v,c; node(){}; node(int form,int to,int cap):u(form),v(to),c(cap){} }; vectoredge; vector G[N]; void Addedge(int u,int v,int cap){ edge.push_back({u,v,cap}); edge.push_back({v,u,0}); int sz=edge.size(); G[u].push_back(sz-2); G[v].push_back(sz-1); } bool bfs(int u){ memset(dis,-1,sizeof(dis)); dis[u]=0; queueq; q.push(u); while(!q.empty()){ int u=q.front(); q.pop(); for(int i=0;i0){ dis[e.v]=dis[u]+1; q.push(e.v); } } } return dis[m]>0; } int dfs(int u,int flow){ if(u==m) return flow; int now; for(int i=0;i0&&dis[u]+1==dis[e.v]&&(now=dfs(e.v,min(flow,e.c)))){ edge[G[u][i]].c-=now; edge[G[u][i]^1].c+=now; return now; } } return 0; } void dinic(){ while(bfs(1)){ int res=0; while(res=dfs(1,INF)){ ans+=res; } } } void init(){ for(int i=1;i<=m;i++)G[i].clear(); edge.clear(); ans=0; } int main() { #ifdef DEBUG freopen("input.in", "r", stdin); //freopen("output.out", "w", stdout); #endif //ios::sync_with_stdio(false); //cin.tie(0); //cout.tie(0); //scanf("%d",&t); //int T=0; while(~scanf("%d%d",&n,&m)){ init(); for(int i=1;i<=n;i++){ scanf("%d%d%d",&u,&v,&w); Addedge(u,v,w); } dinic(); printf("%d\n",ans); } #ifdef DEBUG printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC); #endif //cout << "Hello world!" << endl; return 0; }
