Algo lab/mst

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int n,m;
vector<int> u,v;
vector<int> weights;
vector<pair<int,int>> ew;

void read_input()
{
  cin >> n >> m;
  for(int i=0; i<m; i++) {
    int a,b,w;
    cin >> a >> b >> w;
    a--; b--;
    u.push_back(a);
    v.push_back(b);
    weights.push_back(w);

    ew.push_back(make_pair(w,i));
  }
}

const int MAX_N = 200010;
int parents[MAX_N];
int ranks[MAX_N];
void init_union_find()
{
  for(int i=0; i<n; i++) {
    parents[i] = i;
    ranks[i] = 1;
  }
}
int find(int x) 
{ 
  if(parents[x]==x) {
    return x;
  } else {
    return find(parents[x]);
  }
}
void union_sets(int x, int y) 
{
  if(parents[x] == parents[y]) {
    return;
  }
  int py = find(y);
  int px = find(x);
  if(ranks[px] > ranks[py]) {
    parents[py] = px;
  } else if(ranks[py] > ranks[px]) {
    parents[px] = py;
  } else {
    parents[py] = px;
    ranks[px]++;
  }
}

int main()
{
  read_input();
  sort(ew.begin(), ew.end());
  init_union_find();
   
  int total_weight = 0;

  for(int i=0; i<m; i++) {
    int e = ew[i].second;   //  end points are u[e] and v[e]

    if(find(u[e]) != find(v[e])) {
      // add e to our solution

      total_weight += weights[e];
      union_sets(u[e], v[e]);
    }
  }

  cout << total_weight << endl;
  return 0;
}