HDU 3879 Base Station 最大权闭合子图

#include <cstdio>
#include <algorithm>
#include <cstring>

using namespace std;

struct edge{
int from,to;
int cap,flow;
edge(int u =0,int v =0,int c=0,int f=0):from(u),to(v),cap(c),flow(f){}
};

struct ISAP{
static const int INF = 0x3f3f3f3f;
static const int MAX = 500000 * 2;//2倍的边的大小
int head[MAX];//每个节点对应链表的开始位置
int next[MAX];//链表的下一个节点在edges数组的位置
int tot;//edges数组的大小
edge edges[MAX];//储存边的数组
int que[MAX],front,tail;//队列，保存节点
int d[MAX];//距离标号
bool vis[MAX];//访问标记
int num[MAX];//gap优化
int pre[MAX];//增广路中，节点X的前面一个弧的标号
int cur[MAX];//对于每个节点的，处理的当前弧。
int s,t,n;//s源点标号，t汇点标号，n节点总数
void init(int n){
this->n = n;//注意此处的下标问题
memset(head,-1,sizeof(int)*(n+1));
tot = 0;//
}
void addedge(int from,int to, int cap){
edges[tot] = edge(from,to,cap,0);
next[tot] = head[from], head[from] = tot++;
edges[tot] = edge(to,from,0,0);
next[tot] = head[to],head[to] = tot++;
}
void bfs(){
memset(vis,0,sizeof(vis));
front = tail = 0;
d[t] = 0;
vis[t] = true;
que[tail++] = t;
while(front < tail){
int u = que[front++];
for(int v = head[u]; v != -1; v = next[v]){
edge & e = edges[v^1];
if(e.cap > e.flow && !vis[e.from]){//对处于残余网络中的弧且没访问过的节点处理
d[e.from] = d[u] + 1;
vis[e.from] = true;
que[tail++] = e.from;
}
}
}
}
int augment(){
int x = t,a = INF;
while(x != s){
edge& e = edges[pre[x]];
a = min(a,e.cap - e.flow);
x = e.from;
}

x = t;
while(x != s){
edges[pre[x]].flow += a;
edges[pre[x]^1].flow -= a;
x = edges[pre[x]].from;
}
return a;
}
int maxflow(int s, int t){
this->s = s, this->t = t;
memset(num,0,sizeof(num));
int flow = 0;
bfs();
for(int i = 0; i <= n; ++i){//注意此处的下标问题
num[d[i]]++;
cur[i] = head[i];
}
int x = s;
while(d[s] < n){
if(x == t){
flow += augment();
x = s;
}
bool ok = false;
for(int &v = cur[x]; v != -1; v = next[v]){
edge& e = edges[v];
if(e.cap > e.flow && d[x] == d[e.to] + 1){
ok = true;
pre[x = e.to] = v;
break;
}
}
if(!ok){
int m = n - 1;
for(int v = head[x]; v != -1; v = next[v]){
edge & e = edges[v];
if(e.cap > e.flow) m = min(m,d[e.to]);
}
if(--num[d[x]] == 0) break;
num[d[x]=m+1]++;
cur[x] = head[x];
if(x != s) x = edges[pre[x]].from;
}
}
return flow;
}
} solver;

const int INF = 0x3f3f3f3f;

int main(void)
{
//freopen("main.in","r",stdin);
int N,M,p,a,b,c;
while(scanf("%d %d", &N, &M) != EOF){
solver.init(N + M + 2);
int sum = 0;
int s = 0, t = N + M + 1;
for(int i = 1 ; i <= N; ++i){
scanf("%d", &p);
solver.addedge(i,t,p);
}
for(int i = 1; i <= M; ++i){
scanf("%d %d %d", &a,&b,&c);
solver.addedge(s,N + i,c);
solver.addedge(N + i,a,INF);
solver.addedge(N + i,b,INF);
sum += c;
}
printf("%d\n",sum - solver.maxflow(s,t));
}
return 0;
}