HDU 3879 Base Station(最大权闭合子图)

将第i个用户和他需要的基站连边，转化成求二分图的最大权闭合子图。

答案=正权点之和-最小割。

# include <cstdio>

# include <cstring>

# include <cstdlib>

# include <iostream>

# include <vector>

# include <queue>

# include <stack>

# include <map>

# include <set>

# include <cmath>

# include <algorithm>

using namespace std;

# define lowbit(x) ((x)&(-x))

# define pi 3.1415926535

# define eps 1e-

# define MOD

# define INF

# define mem(a,b) memset(a,b,sizeof(a))

# define FOR(i,a,n) for(int i=a; i<=n; ++i)

# define FO(i,a,n) for(int i=a; i<n; ++i)

# define bug puts("H");

# define lch p<<,l,mid

# define rch p<<|,mid+,r

# define mp make_pair

# define pb push_back

typedef pair<int,int> PII;

typedef vector<int> VI;

# pragma comment(linker, "/STACK:1024000000,1024000000")

typedef long long LL;

int Scan() {

    int res=, flag=;

    char ch;

    if((ch=getchar())=='-') flag=;

    else if(ch>=''&&ch<='') res=ch-'';

    while((ch=getchar())>=''&&ch<='')  res=res*+(ch-'');

    return flag?-res:res;

}

void Out(int a) {

    if(a<) {putchar('-'); a=-a;}

    if(a>=) Out(a/);

    putchar(a%+'');

}

const int N=;

//Code begin...

struct Edge{int p, next, w;}edge[];

int head[N], cnt=, s, t, vis[N];

queue<int>Q;

void add_edge(int u, int v, int w){

    edge[cnt].p=v; edge[cnt].w=w; edge[cnt].next=head[u]; head[u]=cnt++;

    edge[cnt].p=u; edge[cnt].w=; edge[cnt].next=head[v]; head[v]=cnt++;

}

int bfs(){

    int i, v;

    mem(vis,-);

    vis[s]=; Q.push(s);

    while (!Q.empty()) {

        v=Q.front(); Q.pop();

        for (i=head[v]; i; i=edge[i].next) {

            if (edge[i].w> && vis[edge[i].p]==-) {

                vis[edge[i].p]=vis[v] + ;

                Q.push(edge[i].p);

            }

        }

    }

    return vis[t]!=-;

}

int dfs(int x, int low){

    int i, a, temp=low;

    if (x==t) return low;

    for (i=head[x]; i; i=edge[i].next) {

        if (edge[i].w> && vis[edge[i].p]==vis[x]+){

            a=dfs(edge[i].p,min(edge[i].w,temp));

            temp-=a; edge[i].w-=a; edge[i^].w += a;

            if (temp==) break;

        }

    }

    if (temp==low) vis[x]=-;

    return low-temp;

}

int main ()

{

    int n, m, u, v, tmp;

    while (~scanf("%d%d",&n,&m)) {

        s=, t=n+m+;

        int res=, sum=;

        mem(head,); cnt=;

        FOR(i,,n) scanf("%d",&tmp), add_edge(m+i,t,tmp);

        FOR(i,,m) {

            scanf("%d%d%d",&u,&v,&tmp); res+=tmp;

            add_edge(s,i,tmp); add_edge(i,m+u,INF); add_edge(i,m+v,INF);

        }

        while (bfs()) while (tmp=dfs(s,INF)) sum+=tmp;

        printf("%d\n",res-sum);

    }

    return ;

}