1579. Remove Max Number of Edges to Keep Graph Fully Traversable1

#include <bits/stdc++.h>
using namespace std;
class DisjointSetUnion { 
    vector<int> parent;
    vector<int> rank; 
 
public:
    DisjointSetUnion(int n) {
        parent.resize(n);
        rank.resize(n, 0); 
        for (int i = 0; i < n; ++i) {
            parent[i] = i;
        }
    }
 
    int find(int u) {
        if (parent[u] != u) {
            parent[u] = find(parent[u]); // Path compression
        }
        return parent[u];
    }
 
    void unionByRank(int u, int v) {
        int rootU = find(u);
        int rootV = find(v);
        if (rootU != rootV) {
            if (rank[rootU] > rank[rootV]) {
                parent[rootV] = rootU;
            } else if (rank[rootU] < rank[rootV]) {
                parent[rootU] = rootV;
            } else {
                parent[rootV] = rootU;
                rank[rootU]++;
            }
        }
    }
};
 
class Solution {
public:
    int maxNumEdgesToRemove(int n, vector<vector<int>>& e) {
    DisjointSetUnion a(n+1);
    DisjointSetUnion b(n+1);   
    int ans=0;
    for(auto it:e) { 
        if(it[0]==3){ 
            if(a.find(it[1])==a.find(it[2])){ans++; continue; }
            a.unionByRank(it[1],it[2]);
            b.unionByRank(it[1],it[2]);
        } 
    }
    for(auto it:e) {
        if(it[0]!=3){  
            if(it[0]==1){
            if(a.find(it[1])==a.find(it[2])){ans++; continue; }
            a.unionByRank(it[1],it[2]);
            } else {
            if(b.find(it[1])==b.find(it[2])){ans++; continue; }
            b.unionByRank(it[1],it[2]);
            }
        } 
    }
    int k=a.find(1);
    for(int i=1;i<=n;i++){
        if(k!=a.find(i) or k!=b.find(i)){
            return -1;
        } 
    }
    return ans; 
    }
};