ZKW费用流

http://www.artofproblemsolving.com/blog/54262

http://blog.youkuaiyun.com/sdj222555/article/details/7841576

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <cmath>
#include <utility>
using namespace std;
#define REP(i,n)   for(int i=0;i<(n);++i)
#define FOR(i,l,r) for(int i=(l);i<=(r);++i)
#define DSC(i,r,l) for(int i=(r);i>=(l);--i)

#define N 210
#define M 50000
#define INF 1e9
struct ZKW_flow
{
    struct node
    {
        int v,f,c;
    };
    int st, ed, ecnt, n;
    int head[N],next[M];
    node edge[M];

    void init()
    {
        memset(head, -1, sizeof(head));
        ecnt = 0;
    }

    void add(int u, int v, int f, int c)
    {
        edge[ecnt].v=v;
        edge[ecnt].f=f;
        edge[ecnt].c=c;
        next[ecnt]=head[u];
        head[u]=ecnt++;

        edge[ecnt].v=u;
        edge[ecnt].f=0;
        edge[ecnt].c=-c;
        next[ecnt]=head[v];
        head[v]=ecnt++;
    }

    int dis[N];

    void SPFA()
    {
        for(int i=0;i<=n;i++)
            dis[i]=INF;
        queue<pair<int, int> > Q;
        dis[st] = 0;
        Q.push(make_pair(0, st));
        while(!Q.empty())
        {
            int u=Q.front().second,
            d=Q.front().first;
            Q.pop();
            if(dis[u] != d)
                continue;
            for(int i=head[u];i!=-1;i=next[i])
            {
                int &v =edge[i].v;
                if(edge[i].f&&dis[v]>d+edge[i].c)
                {
                    dis[v]=d+edge[i].c;
                    Q.push(make_pair(dis[v], v));
                }
            }
        }
        for(int i=0;i<=n;i++)
            dis[i]=dis[ed]-dis[i];
    }

    int minCost, maxFlow;
    bool use[N];
    int add_flow(int u, int flow)
    {
        if(u == ed)
        {
            maxFlow += flow;
            minCost += dis[st] * flow;
            return flow;
        }
        use[u] = true;
        int now = flow;
        for(int i=head[u];i!=-1;i=next[i])
        {
            int &v =edge[i].v;
            if(edge[i].f&& !use[v]&&dis[u]==dis[v]+edge[i].c)
            {
                int tmp = add_flow(v, min(now,edge[i].f));
                edge[i].f-=tmp;
                edge[i^1].f+=tmp;
                now -= tmp;
                if(!now) break;
            }
        }
        return flow - now;
    }

    bool modify_label()
    {
        int d = INF;
        for(int u = 0; u <= n; u++) if(use[u])
            for(int i = head[u]; i!=-1; i = next[i])
            {
                int &v = edge[i].v;
                if(edge[i].f && !use[v]) d = min(d, dis[v] + edge[i].c - dis[u]);
            }
        if(d == INF) return false;
        for(int i = 0; i <= n; ++i) if(use[i]) dis[i] += d;
        return true;
    }

    int min_cost_flow(int ss, int tt, int nn)
    {
        st = ss, ed = tt, n = nn;
        minCost = maxFlow = 0;
        SPFA();
        while(true)
        {
            while(true)
            {
                for(int i = 0; i <= n; ++i) use[i] = 0;
                if(!add_flow(st, INF)) break;
            }
            if(!modify_label()) break;
        }
        return minCost;
    }
} G;

int main()
{
    int n,m;
    while(cin>>n>>m)
    {
        G.init();
        int start=0,end=n;

        cout<<G.min_cost_flow(start,end,end)<<endl;
    }
    return 0;
}