poj2135最小费用流

#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cassert>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define C 0.5772156649
#define pi acos(-1.0)
#define ll long long
#define mod 20090717
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1

using namespace std;

const double g=10.0,eps=1e-12;
const int N=1000+10,maxn=10000+10,inf=0x3f3f3f3f;

struct edge{
    int to,Next,c;
    int cost;
}e[maxn<<2];
int cnt,head[N];
int s,t;
int dis[N],pre[N],path[N];
void add(int u,int v,int c,int cost)
{
    e[cnt].to=v;
    e[cnt].c=c;
    e[cnt].cost=cost;
    e[cnt].Next=head[u];
    head[u]=cnt++;
    e[cnt].to=u;
    e[cnt].c=0;
    e[cnt].cost=-cost;
    e[cnt].Next=head[v];
    head[v]=cnt++;
}
bool spfa()
{
    memset(pre,-1,sizeof pre);
    memset(dis,inf,sizeof dis);
    dis[s]=0;
    queue<int>q;
    q.push(s);
    while(!q.empty())
    {
        int x=q.front();
        q.pop();
        for(int i=head[x];~i;i=e[i].Next)
        {
            int te=e[i].to;
            if(e[i].c>0&&dis[x]+e[i].cost<dis[te])
            {
                dis[te]=dis[x]+e[i].cost;
                pre[te]=x;
                path[te]=i;
                q.push(te);
            }
        }
    }
    return pre[t]!=-1;
}
int mincostmaxflow()
{
    int cost=0,flow=0;
    while(spfa())
    {
        int f=inf;
        for(int i=t;i!=s;i=pre[i])
            if(e[path[i]].c<f)
               f=e[path[i]].c;
        flow+=f;
        cost+=dis[t]*f;
        for(int i=t;i!=s;i=pre[i])
        {
            e[path[i]].c-=f;
            e[path[i]^1].c+=f;
        }
    }
    return cost;
}
void init()
{
    memset(head,-1,sizeof head);
    cnt=0;
}
int main()
{
   /* ios::sync_with_stdio(false);
    cin.tie(0);*/
    int n,m;
    while(~scanf("%d%d",&n,&m))
    {
        init();
        s=0,t=n+1;
        for(int i=0;i<m;i++)
        {
            int a,b,c;
            scanf("%d%d%d",&a,&b,&c);
            add(a,b,1,c);
            add(b,a,1,c);
        }
        add(0,1,2,0);
        add(n,n+1,2,0);
        printf("%d\n",mincostmaxflow());
    }
    return 0;
}
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