文章标题 HDU 3549 ： Flow Problem （最大流--模板）

题目 链接

求点1到N 的最大流

代码：

#include<iostream>#include<string>#include<cstdio>#include<cstring>#include<vector>#include<math.h>#include<map>#include<queue> #include<algorithm>using namespace std;const int inf = 0x3f3f3f3f;typedef pair<int,int> pii;const int maxn=1006<<1;int n,m;struct node {    int v,nex,cap,flow;};struct Dinic{    int head[maxn];    int st,la;//源点和汇点     int vis[maxn],tot;    node edge[maxn];    void init(){        tot=0;        memset (head,-1,sizeof (head));    }    void addedge(int u,int v,int c){        edge[tot]=node{v,head[u],c,0};        head[u]=tot++;        edge[tot]=node{u,head[v],0,0};        head[v]=tot++;    }     int bfs(){        memset (vis,0,sizeof (vis));        queue<int>q;        q.push(st);        vis[st]=1;        while (!q.empty()){            int u=q.front();q.pop();            for (int i=head[u];i!=-1;i=edge[i].nex){                int v=edge[i].v,cap=edge[i].cap,flow=edge[i].flow;                if(vis[v]==0&&cap>flow){                    vis[v]=vis[u]+1;                    if (v==la){                        return 1;                    }                    q.push(v);                }             }         }        return 0;    }    int dfs(int u,int flow){        if (u==la||flow==0){            return flow;        }        int ans=0,tmp;        for (int i=head[u];i!=-1;i=edge[i].nex){            int v=edge[i].v,cap=edge[i].cap,f=edge[i].flow;            if ((vis[v]==vis[u]+1)&&(tmp=dfs(v,min(cap-f,flow)))>0){                edge[i].flow+=tmp;                edge[i^1].flow-=tmp;                ans+=tmp;                flow-=tmp;                if (flow==0)break;            }        }        return ans;    }    int max_flow(int s,int t){        this->st=s;        this->la=t;        int ans=0;        while (bfs()){            while (1){                int tmp=dfs(st,inf);                if (tmp==0)break;                ans+=tmp;            }        }        return ans;    }}dinic;int main (){    int T;    scanf ("%d",&T);    int cnt=1;    while(T--){        dinic.init();        scanf ("%d%d",&n,&m);        int u,v,c;        for (int i=0;i<m;i++){            scanf ("%d%d%d",&u,&v,&c);            dinic.addedge(u,v,c);        }        printf ("Case %d: %d\n",cnt++,dinic.max_flow(1,n));    }     return 0;}