洛谷P2763 试题库问题 最大流
Code:
#include<cstdio> #include<algorithm> #include<vector> #include<queue> #include<cstring> using namespace std; const int maxn=3000; const int INF=10000000; # define pb push_back int s,t; struct Edge{ int from,to,cap; Edge(int u,int v,int c):from(u),to(v),cap(c) {} }; vector<Edge>edges; vector<int>G[maxn]; struct Dicnic{ int d[maxn],vis[maxn],cur[maxn]; queue<int>Q; void addedge(int u,int v,int c){ edges.pb(Edge(u,v,c)); //正向弧 edges.pb(Edge(v,u,0)); //反向弧 int m=edges.size(); G[u].pb(m-2); G[v].pb(m-1); } int BFS() { memset(vis,0,sizeof(vis)); d[s]=0,vis[s]=1;Q.push(s); while(!Q.empty()){ int u=Q.front();Q.pop(); int sz=G[u].size(); for(int i=0;i<sz;++i){ Edge e=edges[G[u][i]]; if(!vis[e.to]&&e.cap>0){ d[e.to]=d[u]+1,vis[e.to]=1; Q.push(e.to); } } } return vis[t]; } int dfs(int x,int a){ if(x==t)return a; int sz=G[x].size(); int f,flow=0; for(int i=cur[x];i<sz;++i){ Edge e=edges[G[x][i]]; cur[x]=i; if(d[e.to]==d[x]+1&&e.cap>0){ f=dfs(e.to,min(a,e.cap)); if(f) { int u=G[x][i]; a-=f; edges[u].cap-=f; edges[u^1].cap+=f; flow+=f; if(a==0)break; } } } return flow; } int maxflow(){ int ans=0; while(BFS()){ memset(cur,0,sizeof(cur)); ans+=dfs(s,INF); } return ans; } }op; int main() { int k,n;scanf("%d%d",&k,&n); s=0,t=k+n+1; int sum=0; for(int i=1;i<=n;++i)op.addedge(s,i,1); for(int i=1;i<=k;++i) { int a;scanf("%d",&a); sum+=a; op.addedge(n+i,t,a); } for(int i=1;i<=n;++i) { int b;scanf("%d",&b); while(b--) { int a;scanf("%d",&a); op.addedge(i,a+n,1); } } int F=op.maxflow(); if(F!=sum){printf("No Solution!\n");return 0;} for(int u=n+1;u<=n+k;++u) { printf("%d: ",u-n); int sz=G[u].size(); for(int i=0;i<sz;++i) { int e=G[u][i]; if(e%2==1) { if(edges[e].cap==1)printf("%d ",edges[e].to); } } printf("\n"); } return 0; }