graph/Road Reparation at master · jt112/graph · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
//g++  5.4.0

#include<bits/stdc++.h>
using namespace std;

#define int long long
#define pb push_back
#define fast ios::sync_with_stdio(0) , cin.tie(0) , cout.tie(0) ;

const int nax = 1e5+10;
int par[nax] ,sz[nax];

int fp(int v)
{
    if( v==par[v] ) return v;
    return par[v] = fp(par[v]);
}

struct edge_t
{
    int u ,v, w;
    bool operator<(edge_t const &p) const
    {
        return w < p.w;
    }
};

vector<edge_t> e;
signed main()
{
    fast;
    int n , m;
    cin >> n >> m;
    for(int i=1 ; i<=n ; i++ ) par[i] = i , sz[i] = 1;
    for(int i=0 ; i<m ; i++ )
    {
        int u,v,w;
        cin >> u >> v >> w;
        e.pb({u,v,w});
    }
    sort( e.begin() , e.end() );
    int i=0;
    int valid = 0;
    int ans = 0;
    while( i<m && valid< (n-1) )
    {
        int pu = fp(e[i].u);
        int pv = fp(e[i].v);
        if( pu != pv )
        {
            if( sz[pu] > sz[pv] ) swap(pu,pv);
            par[pu] = pv;
            sz[pv] += sz[pu];
            ans += e[i].w;
            valid++;
        }
        i++;
    }
    if( valid == n-1 ) cout << ans << "\n";
    else               cout << "IMPOSSIBLE";
}