HDU 1532 最大流，EK算法

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#include <iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<string>#include<queue>#define N 205#define INF 0x7fffffff#define M 505using namespace std;int head[N],cnt;struct edge{    int to,next,cap;}e[M];void init(){    cnt=0;    memset(head,-1,sizeof(head));}void addedge(int u,int v,int cap){    e[cnt].to=v;e[cnt].cap=cap;e[cnt].next=head[u];head[u]=cnt++;    e[cnt].to=u;e[cnt].cap=0;e[cnt].next=head[v];head[v]=cnt++;}int pre[N],pe[N];queue<int> q;int EK(int s,int t){    int max_flow=0;    while(true){        while(!q.empty()){            q.pop();        }        memset(pre,-1,sizeof(pre));        q.push(s);        while(!q.empty()){            int u=q.front();            q.pop();            for(int i=head[u];i!=-1;i=e[i].next){                int v=e[i].to;                if(pre[v]==-1&&e[i].cap>0){                    q.push(v);                    pre[v]=u;                    pe[v]=i;                }            }            if(pre[t]!=-1)            break;        }        if(pre[t]==-1)        break;        int aug=INF;        for(int v=t;v!=s;v=pre[v]){            aug=min(aug,e[pe[v]].cap);        }        for(int v=t;v!=s;v=pre[v]){            e[pe[v]].cap-=aug;            e[pe[v]^1].cap+=aug;        }        max_flow+=aug;    }    return max_flow;}int main(){    int n,m,u,v,cap,ans;    while(~scanf("%d%d",&m,&n)){        init();        while(m--){            scanf("%d%d%d",&u,&v,&cap);            addedge(u,v,cap);        }        ans=EK(1,n);        printf("%d\n",ans);    }    return 0;}
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