luogu p4174 最大获利（最大权闭合子图）

#include <cstdio> 
#include <cstring>
using namespace std;

const int maxn=1e5+5, maxm=2e5+5, INF=1e9;
int n, m, src, dst, ans;
inline int min(int x, int y){ return x<y?x:y; }

struct Edge{
    int to, nxt, f;
}e[maxm*2];
int fir[maxn], cnte=1;
void addedge(int x, int y, int v){
    Edge &ed=e[++cnte];
    ed.to=y; ed.nxt=fir[x]; ed.f=v; fir[x]=cnte; 
}

int q[maxn], head, tail, dep[maxn];
bool bfs(){
    memset(dep, 0, sizeof(dep)); dep[src]=1;
    head=tail=0; q[tail++]=src; int u;
    while (head<tail){
        u=q[head++];
        for (int i=fir[u]; ~i; i=e[i].nxt)
            if (e[i].f&&!dep[e[i].to]){
                dep[e[i].to]=dep[u]+1;
                q[tail++]=e[i].to;
            }
    }
    return dep[dst];
}

int cur[maxn];
int dfs(int u, int flow){
    if (u==dst) return flow;
    for (int i=cur[u]; ~i; i=e[i].nxt, cur[u]=i)
    if (dep[e[i].to]==dep[u]+1&&e[i].f){
        int minm=dfs(e[i].to, min(flow, e[i].f));
        e[i].f-=minm; e[i^1].f+=minm;
        if (minm) return minm;
    }
    return 0;
}

int Dinic(){
    int ans=0, t;
    while (bfs()){
        memcpy(cur, fir, sizeof(fir));
        while (t=dfs(src, INF)) ans+=t; 
    }
    return ans;
}

int main(){
    memset(fir, -1, sizeof(fir));
    scanf("%d%d", &n, &m); int t, ta, tb;
    src=0; dst=n+m+1;
    for (int i=1; i<=n; ++i){
        scanf("%d", &t);
        addedge(src, i, t); addedge(i, src, 0);
    }
    for (int i=1; i<=m; ++i){
        scanf("%d%d%d", &ta, &tb, &t); ans+=t;
        addedge(ta, i+n, INF); addedge(i+n, ta, 0);
        addedge(tb, i+n, INF); addedge(i+n, tb, 0);
        addedge(i+n, dst, t); addedge(dst, i+n, 0);
    }
    ans-=Dinic();
    printf("%d\n", ans);
    return 0;
}