POJ 1679 The Unique MST(次小生成树)

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
using namespace std ;
typedef long long LL ;
const int N = 110;
const int M = 11000;
struct edge {
    int u , v , w ;
    bool operator < ( const edge &a ) const {
        return w < a.w ;
    }
}e[M];
int n , m , fa[N] , cnt ;
bool vis[M] ;
int find( int k ) { return k == fa[k] ? k : find(fa[k]); }
int mst( int ban  ) {
    int ans = 0 ; cnt = 0 ;
    for( int i = 0 ; i <= n ; ++i ) fa[i] = i ;
    for( int i = 0 ; i < m ; ++i ) {
        int fu = find( e[i].u ) , fv = find( e[i].v );
        if( fu == fv || i == ban ) continue ;
        fa[fv] = fu;
        ans += e[i].w ;
        if( ban == -1 ) vis[i] = true ;
        cnt++ ;
    }
    return ans ;
}

void Work() {
    sort( e , e + m );
    memset( vis , false , sizeof vis );
    int ans = mst( -1 );
    for( int i = 0 ; i < m ; ++i ) if( vis[i] ) {
        if( mst(i) == ans && cnt == n - 1 ) {
            cout << "Not Unique!" << endl ;
            return ;
        }
    }
    cout << ans << endl ;
}

int main ()  {
//    freopen("in.txt","r",stdin);
    int _ ; cin >> _ ;
    while( _-- ) {
        cin >> n >> m ;
        for( int i = 0 ; i < m ; ++i ) {
            cin >> e[i].u >> e[i].v >> e[i].w ;
        }
        Work();
    }
}