zoj-3792-Romantic Value-最小割+数值转化

来源：互联网发布：淘宝文案招聘编辑：程序博客网时间：2024/05/18 14:26
如果不需要求边的个数的话，就是一个裸的最小割问题。
求边的个数就用边的权值记录一下。
#include <stdio.h>#include <iostream>#include <algorithm>#include <string.h>#include<queue>using namespace std;#define INF 99999999#define LL long longconst LL maxn =55;const LL maxm =4400;const LL oo = (LL)1<<37;struct Arclist{    LL cnt, head[maxn], dis[maxn];    LL cur[maxn], pre[maxn], gap[maxn], aug[maxn];    struct node    {        LL u, v, w, next;    }edge[maxm];    void init()    {        cnt = 0;        memset(head,-1,sizeof(head));    }    void add(LL u, LL v, LL w)    {       // cout<<u<<" "<<v<<" "<<w<<endl;        edge[cnt].u = u;        edge[cnt].v = v;        edge[cnt].w = w;        edge[cnt].next = head[u];        head[u] = cnt++;        edge[cnt].u = v;        edge[cnt].v = u;        edge[cnt].w = 0;        edge[cnt].next = head[v];        head[v] = cnt++;    }    LL sap(LL s, LL e, LL n)    {        LL max_flow = 0, u = s;        LL mindis;        for(LL i = 0; i <= n; i++)        {            cur[i] = head[i];            dis[i] = 0;            gap[i] = 0;        }        aug[s] = oo;        pre[s] = -1;        gap[0] = n;        while(dis[s]<n)        {            bool flag = false;            if(u==e)            {                max_flow += aug[e];                for(LL v = pre[e]; v != -1; v = pre[v])                {                    LL id = cur[v];                    edge[id].w -= aug[e];                    edge[id^1].w += aug[e];                    aug[v] -= aug[e];                    if(edge[id].w==0) u = v;                }            }            for(LL id = cur[u]; id != -1; id = edge[id].next)            {                LL v = edge[id].v;                if(edge[id].w>0 && dis[u]==dis[v]+1)                {                    flag = true;                    pre[v] = u;                    cur[u] = id;                    aug[v] = std::min(aug[u], edge[id].w);                    u = v;                    break;                }            }            if(flag==false)            {                if(--gap[dis[u]]==0) break;                mindis = n;                cur[u] = head[u];                for(LL id = head[u]; id != -1; id = edge[id].next)                {                    LL v = edge[id].v;                    if(edge[id].w>0 && dis[v]<mindis)                    {                        mindis = dis[v];                        cur[u] = id;                    }                }                dis[u] = mindis+1;                ++gap[dis[u]];                if(u!=s) u = pre[u];            }        }        return max_flow;    }}G;int main(){    LL m,n,u,v,w,T,st,ed;    scanf("%lld",&T);    while(T--)    {        scanf("%lld%lld%lld%lld",&n,&m,&st,&ed);        G.init();        LL all=0;        while(m--)        {            scanf("%lld%lld%lld",&u,&v,&w);            G.add(v,u,w*1000+1);            G.add(u,v,w*1000+1);            all+=w;        }        LL w=G.sap(st,ed,n);       // cout<<w<<endl;        if(w==0)cout<<"Inf"<<endl;        else        {            double x,y;            if(w%1000==0)            {                y=1000;                w=w-1000;            }            else y=w%1000;            x=all-w/1000;            printf("%.2f\n",1.0*x/y);        }    }    return 0;}
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