hdu_3549_Flow Problem(最大流)

来源：互联网发布：购买海关数据编辑：程序博客网时间：2024/05/22 07:05

题目连接：http://acm.hdu.edu.cn/showproblem.php?pid=3549

题意：求1到n的最大流

题解：模版题，直接上Claris的ISAP，效率是一般dfs的十倍，ORZ Claris!!!

#include<cstdio>#include<algorithm>#define F(i,a,b) for(int i=a;i<=b;i++)using namespace std;const int N=20,inf=~0U>>2,M=2010;struct edge{int t,f;edge*nxt,*pair;}*g[N],*d[N],pool[M],*cur=pool;struct ISAP{int n,m,i,S,T,h[N],gap[N],maxflow;void init(int ss,int tt){for(S=ss,T=tt,cur=pool,i=1;i<=T;i++)g[i]=d[i]=NULL,h[i]=gap[i]=0;}void add(int s,int t,int f){edge*p=cur++;p->t=t,p->f=f,p->nxt=g[s],g[s]=p;p=cur++,p->t=s,p->f=0,p->nxt=g[t],g[t]=p;g[s]->pair=g[t],g[t]->pair=g[s];}int sap(int v,int flow){if(v==T)return flow;int rec=0;for(edge*p=d[v];p;p=p->nxt)if(h[v]==h[p->t]+1&&p->f){int ret=sap(p->t,min(flow-rec,p->f));p->f-=ret;p->pair->f+=ret;d[v]=p;if((rec+=ret)==flow)return flow;}if(!(--gap[h[v]]))h[S]=T;gap[++h[v]]++;d[v]=g[v];return rec;}int get_ans(){for(gap[maxflow=0]=T,i=1;i<=T;i++)d[i]=g[i];while(h[S]<T)maxflow+=sap(S,inf);return maxflow;}}G;int main(){int t,n,m,x,y,c,ic=1;scanf("%d",&t);while(t--){scanf("%d%d",&n,&m);//点，边G.init(1,n);F(i,1,m)scanf("%d%d%d",&x,&y,&c),G.add(x,y,c);printf("Case %d: %d\n",ic++,G.get_ans());}}

0 0