Instant View Of Big Bang Uva

#include<bits/stdc++.h>
using namespace std;
int main(){
    int t;
    cin>>t;
    for(int a=1;a<=t;a++){
        int n,m;
        vector<pair<int,int> >out[1001];
        vector<int>in[1001];
        cin>>n>>m;
        int x,y,t;
        vector<int>v;
        for(int i=0;i<m;i++){
            cin>>x>>y>>t;
            out[x+1].push_back(make_pair(y+1,t));
            in[y+1].push_back(x+1);
        }
        for(int i=0;i<n;i++){
            out[0].push_back(make_pair(i+1,0));
            in[i+1].push_back(0);
        }
        int dist[1001];
        for(int i=1;i<=n;i++)dist[i] = INT_MAX;
        dist[0]=0;
        bool f =false;
        for(int i=0;i<n;i++){
            bool flag = false;
            for(int j=0;j<=n;j++){
                for(int k=0;k<out[j].size();k++){
                    if(dist[out[j][k].first]>dist[j]+out[j][k].second){
                        flag = true;
                        dist[out[j][k].first] = dist[j]+out[j][k].second;
                    }
                }
            }
            if(!flag){
                cout<<"Case "<<a<<": impossible"<<endl;
                f =true;
                break;
            }
        }
        if(f)continue;
        int source =-1;
        for(int j=0;j<=n;j++){
            for(int k=0;k<out[j].size();k++){
                int u = out[j][k].first;
                int weight = out[j][k].second;
        //      cout<<u<<" "<<dist[u]<<" "<<j<<" "<<dist[j]+weight<<endl;
                if(dist[u]>dist[j]+weight){
                    source = u;
                    break;
                }
            }
            if(source!=-1)break;
        }
        if(source==-1){
            cout<<"Case "<<a<<": impossible"<<endl;
            continue;
        }
        bool visited[1001];
        for(int i=0;i<=n;i++)visited[i] = false;
        queue<int>q;
        q.push(source);
        while(!q.empty()){
            int u   = q.front();
            visited[u] = true;
            q.pop();
            v.push_back(u);
            for(int i=0;i<in[u].size();i++){
                if(!visited[in[u][i]] && in[u][i]!=0){
                    q.push(in[u][i]);
                }
            }
        }
        sort(v.begin(),v.end());
        cout<<"Case "<<a<<": ";
        for(int i=0;i<v.size();i++){
            if(i==0)cout<<v[i]-1;
            else cout<<" "<<v[i]-1;
        }
        cout<<endl;
    }
}