HDU 3879 Base Station
Base Station
This problem will be judged on HDU. Original ID: 3879
64-bit integer IO format: %I64d Java class name: Main
When complete building, two places which both have stations can communicate with each other.
Besides,
according to the marketing department, the company has received m
requirements. The ith requirement is represented by three integers Ai, Bi and Ci, which means if place Ai and Bi can communicate with each other, the company will get Ci profit.
Now,
the company wants to maximize the profits, so maybe just part of the
possible locations will be chosen to build new stations. The boss wants
to know the maximum profits.
Input
The first line has two integers n (0<n<=5000) and m (0<m<=50000).
The second line has n integers, P1 through Pn, describes the cost of each location.
Next m line, each line contains three integers, Ai, Bi and Ci, describes the ith requirement.
Output
Sample Input
5 5
1 2 3 4 5
1 2 3
2 3 4
1 3 3
1 4 2
4 5 3
Sample Output
4
Source
#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int maxn = ;
struct arc{
int to,flow,next;
arc(int x = ,int y = ,int z = -){
to = x;
flow = y;
next = z;
}
}e[];
int head[maxn],d[maxn],gap[maxn],tot,S,T;
void add(int u,int v,int flow){
e[tot] = arc(v,flow,head[u]);
head[u] = tot++;
e[tot] = arc(u,,head[v]);
head[v] = tot++;
}
queue<int>q;
void bfs(){
for(int i = ; i <= T; ++i){
d[i] = -;
gap[i] = ;
}
d[T] = ;
q.push(T);
while(!q.empty()){
int u = q.front();
q.pop();
++gap[d[u]];
for(int i = head[u]; ~i; i = e[i].next){
if(d[e[i].to] == -){
d[e[i].to] = d[u] + ;
q.push(e[i].to);
}
}
}
}
int dfs(int u,int low){
if(u == T) return low;
int tmp = ,minH = T - ;
for(int i = head[u]; ~i; i = e[i].next){
if(e[i].flow && d[e[i].to] + == d[u]){
int a = dfs(e[i].to,min(low,e[i].flow));
e[i].flow -= a;
e[i^].flow += a;
low -= a;
tmp += a;
if(!low) break;
if(d[S] >= T) return tmp;
}
if(e[i].flow) minH = min(minH,d[e[i].to]);
}
if(!tmp){
if(--gap[d[u]] == ) d[S] = T;
++gap[d[u] = minH + ];
}
return tmp;
}
int sap(int ret = ){
bfs();
while(d[S] < T) ret += dfs(S,INF);
return ret;
}
int main(){
int n,m,u,v,w;
while(~scanf("%d%d",&n,&m)){
memset(head,-,sizeof head);
int sum = tot = ;
S = n + m + ;
T = S + ;
for(int i = ; i <= n; ++i){
scanf("%d",&w);
add(S,i,w);
}
for(int i = ; i <= m; ++i){
scanf("%d%d%d",&u,&v,&w);
sum += w;
add(u,i + n,INF);
add(v,i + n,INF);
add(i + n,T,w);
}
printf("%d\n",sum-sap());
}
return ;
}
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