POJ2584 T-Shirt Gumbo——网络最大流模板

题目：http://poj.org/problem?id=2584

像模板一样的简单题。继续使用 & 的当前弧优化和神奇的构造函数。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;
int n,head[30],dfn[30],cur[30],l,r,mxflow,xnt,x,t;
const int INF=30;
char tmp[15],tm1,tm2;
struct Edge{
    int next,to,cap;
    Edge(int a=0,int b=0,int c=0):next(a),to(b),cap(c) {}
}edge[255];
queue<int> q;
int num(char c)
{
    if(c=='S')return 1+n;if(c=='L')return 3+n;
    if(c=='M')return 2+n;if(c=='X')return 4+n;if(c=='T')return 5+n;
}
bool bfs()
{
    memset(dfn,0,sizeof dfn);
    while(!q.empty())q.pop();
    dfn[0]=1;
    q.push(0);
    while(!q.empty())
    {
        int k=q.front();q.pop();
        for(int i=head[k],v;i;i=edge[i].next)
            if(!dfn[v=edge[i].to]&&edge[i].cap)
            {
                dfn[v]=dfn[k]+1;
                q.push(v);
                if(v==t)break;
            }
    }
    return dfn[t];
}
int dfs(int k,int flow)
{
    if(k==t)return flow;
    int used=0;
    for(int& i=cur[k],v;i;i=edge[i].next)
        if(dfn[v=edge[i].to]==dfn[k]+1&&edge[i].cap)
        {
            int tmp=dfs(v,min(flow-used,edge[i].cap));
            if(!tmp)dfn[v]=0;
            used+=tmp;
            edge[i].cap-=tmp;
            edge[i^1].cap+=tmp;
            if(used==flow)return used;
        }
    return used;
}
int main()
{
    while(1)
    {
        cin>>tmp;
        if(tmp[0]=='E')return 0;
        scanf("%d ",&n);
        memset(head,0,sizeof head);
        t=n+6;mxflow=0;xnt=1;
        for(int i=1;i<=n;i++)
        {
            edge[++xnt]=Edge(head[0],i,1);head[0]=xnt;
            edge[++xnt]=Edge(head[i],0,0);head[i]=xnt;
            scanf("%c%c ",&tm1,&tm2);
            l=num(tm1);r=num(tm2);
            for(int j=l;j<=r;j++)
            {
                edge[++xnt]=Edge(head[i],j,1);head[i]=xnt;
                edge[++xnt]=Edge(head[j],i,0);head[j]=xnt;
            }
        }
        for(int i=1+n;i<=5+n;i++)
        {
            scanf("%d",&x);
            edge[++xnt]=Edge(head[i],t,x);head[i]=xnt;
            edge[++xnt]=Edge(head[t],i,0);head[t]=xnt;
        }
        cin>>tmp;
        while(bfs())
        {
            memcpy(cur,head,sizeof head);
            mxflow+=dfs(0,INF);
        }
        if(mxflow==n)
            printf("T-shirts rock!
");
        else printf("I'd rather not wear a shirt anyway...
");
    }
}