【网络流#3】hdu 1532 - Dinic模板题

输入为m,n表示m条边，n个结点

记下来m行，每行三个数，x,y,c表示x到y的边流量最大为c

这道题的模板来自于网络

http://blog.csdn.net/sprintfwater/article/details/7913061

算法时间复杂度o(V^2*E)

 

关于这个模板：
Edge为前向星的边数，所以需要初始化Edge和head数组，其中head数组应初始化为-1

int dinic(int n,int s,int t);
n表示有n个点，这个版无所谓点从0开始还是从1开始，s表示源点，t表示汇点
很好的一个是，这个版的DFS使用的是模拟栈，防止爆栈

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#include<cstdio> #include<cstring> #include<cmath> #include<iostream> #include<algorithm> #include<set> #include<map> #include<stack> #include<vector> #include<queue> #include<string> #include<sstream> #define MAXN 200 #define MAXM 400 #define INF (1<<30) #define eps 0.000001 #define ALL(x) x.begin(),x.end() #define INS(x) inserter(x,x.begin()) using namespace std; int i,j,k,n,m,x,y,T,num,w;   const int inf = 0x3f3f3f3f; struct edgenode {     int from,to,next;     int cap; }edge[MAXM]; int Edge,head[MAXN],ps[MAXN],dep[MAXN];   void addedge(int x,int y,int c) {     edge[Edge].from=x;     edge[Edge].to=y;     edge[Edge].cap=c;     edge[Edge].next=head[x];     head[x]=Edge++;           edge[Edge].from=y;     edge[Edge].to=x;     edge[Edge].cap=0;     edge[Edge].next=head[y];     head[y]=Edge++; }   int dinic(int n,int s,int t) {     int tr,flow=0;     int i,j,k,l,r,top;     while(1){         memset(dep,-1,(n+1)*sizeof(int));         for(l=dep[ps[0]=s]=0,r=1;l!=r;)//BFS部分，将给定图分层         {             for(i=ps[l++],j=head[i];j!=-1;j=edge[j].next)             {                 if (edge[j].cap&&-1==dep[k=edge[j].to])                 {                     dep[k]=dep[i]+1;ps[r++]=k;                     if(k==t)                     {                         l=r;                         break;                     }                 }             }         }         if(dep[t]==-1)break;                   for(i=s,top=0;;)//DFS部分         {             if(i==t)//当前点就是汇点时             {                 for(k=0,tr=inf;k<top;++k)                     if(edge[ps[k]].cap<tr)tr=edge[ps[l=k]].cap;                                       for(k=0;k<top;++k)                     edge[ps[k]].cap-=tr,edge[ps[k]^1].cap+=tr;                                       flow+=tr;                 i=edge[ps[top=l]].from;             }                           for(j=head[i];j!=-1;j=edge[j].next)//找当前点所指向的点                 if(edge[j].cap&&dep[i]+1==dep[edge[j].to]) break;                               if(j!=-1)             {                 ps[top++]=j;//当前点有所指向的点，把这个点加入栈中                 i=edge[j].to;             }             else             {                 if (!top) break;//当前点没有指向的点，回溯                 dep[i]=-1;                 i=edge[ps[--top]].from;             }         }     }     return flow; }   int main() {     int T,cas,m,s,t,n,maxflow,i;     int x,y,c;     double ans;     while(~scanf("%d%d",&m,&n))     {           memset(head,-1,sizeof(head));         Edge=0;         for(i=0;i<m;i++)         {             scanf("%d%d%d",&x,&y,&c);             addedge(x,y,c);         }         printf("%d\n",dinic(n,1,n));     }     return 0; }