zoj-3792-Romantic Value-最小割+数值转化

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include<queue>
using namespace std;
#define INF 99999999
#define LL long long
const 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;
}