题目链接:http://acm.hdu.edu.cn/showproblem.php?pid=4292
题解:建一超级源点 汇点, 源点与食物相连边权为其数量,汇点与饮料相连 边权也为其数量 把人分成两个点 之间的边权为1 每个人与之需要的食物和饮料相连 边权为1。
#include <cstdio> #include <cstring> #define INF 0x3f3f3f3f #define MAXN 802 #define MAXE 1000002 using namespace std; struct node { int to,cap,next; }edge[MAXE]; int n,src,dest,tot,pre[MAXN],cur[MAXN]; int head[MAXN],level[MAXN],gap[MAXN],Queue[MAXN]; void addEdge(int u,int v,int w) { edge[tot].to=v; edge[tot].cap=w; edge[tot].next=head[u]; head[u]=tot++; edge[tot].to=u; edge[tot].cap=0; edge[tot].next=head[v]; head[v]=tot++; } void BFS() { int u,v,i,front,rear; memset(level,-1,sizeof(level)); memset(gap,0,sizeof(gap)); level[dest]=0; ++gap[0]; front=rear=0; Queue[rear++]=dest; while(front<rear) { u=Queue[front++]; for(i=head[u];i!=-1;i=edge[i].next) { v=edge[i].to; if(level[v]!=-1) continue; level[v]=level[u]+1; ++gap[level[v]]; Queue[rear++]=v; } } } int ISAP() { int u,v,flag,aug,minlevel,maxflow=0; BFS(); memset(pre,-1,sizeof(pre)); memcpy(cur,head,sizeof(head)); aug=INF; u=pre[src]=src; gap[0]=n; while(level[src]<n) { flag=0; for(int &i=cur[u];i!=-1;i=edge[i].next) { v=edge[i].to; if(edge[i].cap>0&&level[u]==level[v]+1) { flag=1; pre[v]=u; u=v; aug=aug<edge[i].cap?aug:edge[i].cap; if(v==dest) { maxflow+=aug; for(u=pre[v];v!=src;v=u,u=pre[u]) { edge[cur[u]].cap-=aug; edge[cur[u]^1].cap+=aug; } aug=INF; } break; } } if(flag) continue; minlevel=n; for(int i=head[u];i!=-1;i=edge[i].next) { v=edge[i].to; if(edge[i].cap>0&&level[v]<minlevel) { cur[u]=i; minlevel=level[v]; } } if(--gap[level[u]]==0) break; level[u]=minlevel+1; ++gap[level[u]]; u=pre[u]; } return maxflow; } int main() { int N,F,D,i,j,x,num; char str[202]; while(scanf("%d %d %d",&N,&F,&D)!=EOF) { src=F+2*N+D+1; dest=src+1; tot=0; memset(head,-1,sizeof(head)); for(i=1;i<=F;++i) { scanf("%d",&x); addEdge(src,i,x); } num=F+2*N; for(i=1;i<=D;++i) { scanf("%d",&x); addEdge(num+i,dest,x); } for(i=1;i<=N;++i) { addEdge(F+i,F+N+i,1); } for(i=1;i<=N;++i) { scanf("%s",str); for(j=1;j<=F;++j) { if(str[j-1]=='Y') addEdge(j,F+i,1); } } for(i=1;i<=N;++i) { scanf("%s",str); for(j=1;j<=D;++j) { if(str[j-1]=='Y') addEdge(F+N+i,num+j,1); } } n=dest; num=ISAP(); printf("%d\n",num); } return 0; }