HDU 4240 Route Redundancy

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模板题。
只需要在找路径减去流量的过程中找到那个最大的就行了。
#include <iostream>#include <cstdio>#include <cstring>#include <cmath>#include <set>#include <vector>#include <map>#include <queue>#include <set>#include <algorithm>#include <limits.h>using namespace std;#define MAXN 1500#define MAXM 600000const int INF = INT_MAX;typedef long long LL;struct Edge{    int from,to,ci,next;    Edge(){}    Edge(int _from,int _to,int _ci,int _next):from(_from),to(_to),ci(_ci),next(_next){}}e[MAXM];int head[MAXN],tot;int dis[MAXN];int top,sta[MAXN],cur[MAXN];int n,m,maxx=0;inline void init(){    memset(head,-1,sizeof(head));    tot=0;}inline void AddEdge(int u,int v,int ci0,int ci1=0){    e[tot]=Edge(u,v,ci0,head[u]);    head[u]=tot++;    e[tot]=Edge(v,u,ci1,head[v]);    head[v]=tot++;}inline bool bfs(int st,int et){    memset(dis,0,sizeof(dis));    dis[st]=1;    queue <int> q;    q.push(st);    while(!q.empty()){        int now=q.front();        q.pop();        for(int i=head[now];i!=-1;i=e[i].next){            int next=e[i].to;            if(e[i].ci&&!dis[next]){                dis[next]=dis[now]+1;                if(next==et)return true;                q.push(next);            }        }    }    return false;}int Dinic(int st,int et){    int ans=0;    while(bfs(st,et)){        //printf("here\n");        top=0;        memcpy(cur,head,sizeof(head));        int u=st,i;        while(1){            if(u==et){                int pos,minn=INF;                //printf("top:%d\n",top);                for(i=0;i<top;i++)                {                    if(minn>e[sta[i]].ci){                        minn=e[sta[i]].ci;                        pos=i;                    }                    //printf("%d --> %d\n",e[sta[i]].from,e[sta[i]].to);                }                for(i=0;i<top;i++){                    e[sta[i]].ci-=minn;                    e[sta[i]^1].ci+=minn;                }                top=pos;                u=e[sta[top]].from;                ans+=minn;                if(minn>maxx)maxx=ans;                //printf("minn:%d\n\n",minn);            }            for(i=cur[u];i!=-1;cur[u]=i=e[i].next)                if(e[i].ci&&dis[u]+1==dis[e[i].to])break;            if(cur[u]!=-1){                sta[top++]=cur[u];                u=e[cur[u]].to;            }            else {                if(top==0)break;                dis[u]=0;                u=e[sta[--top]].from;            }        }    }    return ans;}int main() {    int t,d,n,m,a,b;    scanf("%d",&t);    while(t--)    {        scanf("%d%d%d%d%d",&d,&n,&m,&a,&b);        init();        for(int i=0,x,y,wi;i<m;i++)        {            scanf("%d%d%d",&x,&y,&wi);            AddEdge(x,y,wi);        }        maxx=0;        int tt=Dinic(a,b);        //printf("tt:%d maxx:%d\n",tt,maxx);        //double ans=(double)Dinic(a,b)/maxx;        double ans=(double)tt/maxx;        printf("%d %.3lf\n",d,ans);    }    return 0;}
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