学步园

常规题目；

最小费用最大流，如果是无向图的话，一定用邻接表去做。

代码：

//最小费用最大流，注意建图的edge都是双向的
#include <cstdio>
#include <cstring>
#include <queue>
#include <iostream>
using namespace std;

const int INF = 0x3fffffff;
const int N = 350;
int S = 0, E;
int n, m, k, p, id;
int head[N], pre[N], r[N];
struct Edge {
    int u, v, w, cap, flow, next;
}e[200000];
void add( int u, int v, int w, int cap, int flow ) {
    e[id].next = head[u], e[id].u = u, e[id].v = v, e[id].w = w, e[id].cap = cap, e[id].flow = 0;
    head[u] = id++;
    e[id].next = head[v], e[id].u = v, e[id].v = u, e[id].w = -w, e[id].cap = 0, e[id].flow = 0;
}
int maxFlow()
{
    bool vis[N];
    int d[N];
    int c = 0, f = 0;
    queue <int> q;
    while ( 1 ) {
        for ( int i = 0; i <= E; ++i ) d[i] = INF;
        d[S] = 0;
        memset( vis, 0, sizeof(vis) );
        vis[S] = true;
        q.push( S );
        while ( !q.empty() ) {
            int u = q.front(); q.pop();
            vis[u] = false;
            for ( int i = head[u]; i != -1; i = e[i].next ) {
                int v = e[i].v, cap = e[i].cap, flow = e[i].flow, w = e[i].w;
                if ( cap > flow && d[v] > d[u] + w ) {
                    d[v] = d[u] + w;
                    pre[v] = u;
                    r[v] = i;
                    if ( !vis[v] ) {
                        vis[v] = true;
                        q.push(v);
                    }
                }
            }
        }
        if ( d[E] == INF ) break;
        int a = INF;
        for ( int u = E; u != S; u = pre[u] ) {
            int ei = r[u];
            a = min( a, e[ei].cap - e[ei].flow );
        }
        for ( int u = E; u != S; u = pre[u] ) {
            int ei = r[u];
            e[ei].flow += a;
            e[ei^1].flow -= a;
        }
        c += d[E]*a;
        f += a;
    }
    return c;
}

int main()
{
    while ( scanf("%d%d%d%d", &n, &m, &k, &p) != EOF ) {
        memset( head, -1, sizeof(head));
        E = n + m + 1;
        id = 0;
        for ( int i = 1, s; i <= n; ++i ) {
            scanf("%d", &s);
            add( S, s, 0, 1, 0 );
            add( s, S, 0, 0, 0 );
        }
        for ( int i = 1, s, e, w; i <= k; ++i) {
            scanf("%d%d%d", &s, &e, &w);
            add( s, e, w, INF, 0 );
            add( s, e, w, INF, 0 );
        }
        for ( int i = 1, s, e, w; i <= p; ++i) {
            scanf("%d%d%d", &s, &e, &w);
            add( s+m, e, w, INF, 0 );
            add( e, s+m, w, INF, 0 ); 
        }
        for ( int i = m+1; i <= m+n; ++i ) {
            add( i, E, 0, 1, 0 );
            add( E, i, 0, 0, 0 );
        }
        printf("%d\n", maxFlow());
    }
}