hdu4292 Food (ISAP算法)

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 1000002using 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;}