Nick's company employed n people. Now Nick needs to build a tree hierarchy of «supervisor-surbodinate» relations in the company (this is to say that each employee, except one, has exactly one supervisor). There are m applications written in the following form: «employee ai is ready to become a supervisor of employee bi at extra cost ci». The qualification qj of each employee is known, and for each application the following is true: qai > qbi.
Would you help Nick calculate the minimum cost of such a hierarchy, or find out that it is impossible to build it.
The first input line contains integer n (1 ≤ n ≤ 1000) — amount of employees in the company. The following line contains n space-separated numbers qj (0 ≤ qj ≤ 106)— the employees' qualifications. The following line contains number m (0 ≤ m ≤ 10000) — amount of received applications. The following mlines contain the applications themselves, each of them in the form of three space-separated numbers: ai,bi and ci (1 ≤ ai, bi ≤ n, 0 ≤ ci ≤ 106). Different applications can be similar, i.e. they can come from one and the same employee who offered to become a supervisor of the same person but at a different cost. For each application qai > qbi.
Output the only line — the minimum cost of building such a hierarchy, or -1 if it is impossible to build it.
47 2 3 141 2 52 4 13 4 11 3 5
11
31 2 323 1 23 1 3
-1
In the first sample one of the possible ways for building a hierarchy is to take applications with indexes 1, 2 and 4, which give 11 as the minimum total cost. In the second sample it is impossible to build the required hierarchy, so the answer is -1.
#include#include #include #include #include using namespace std;const int INF=0x3ffffff;int f[1100];int main(){ int n,m; int temp,u,v,w; while(cin>>n) { for(int i=1;i<=n;i++) { cin>>temp; f[i]=INF; } cin>>m; for(int i=1;i<=m;i++) { cin>>u>>v>>w; if(f[v]>w)//预处理最小值 f[v]=w; } int flag=1,k=1; int ans=0; for(int i=1;i<=n;i++)//仅仅能有一个INF,即根节点 { if(f[i]==INF&&k) { ans-=INF; k=0; } else if(f[i]==INF) { flag=0; break; } ans+=f[i]; } if(flag) cout< <