Codeforces-Solutions/A_Ice_Skating.cpp at main · govinddwivedi-git/Codeforces-Solutions · GitHub

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

// Macros and constants
#define endl ("\n")
#define pi (3.141592653589)
#define int long long
#define float double
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define all(c) c.begin(), c.end()
#define mini(a, b, c) min(c, min(a, b))
#define mini2(a, b, c, d) min(d, min(c, min(a, b)))
#define rrep(i,s,n) for(int i=n-1;i>=s;i--)
#define rep(i,n) for(int i=0;i<n;i++)
#define fast ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#define scin(str) getline(cin, str)

// Debugging Macros
#define debug(x) cerr << #x << " = " << x << endl
#define debug2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl

// Aliases and Types
using vec = vector<int>;
using pii=pair<int,int>;
using mapi=map<int,int>;
using si=set<int>;

const int mod = 1e9+7;

class DisjointSet {
    public:
    vector<int> rank, parent, size;
    DisjointSet(int n) {
        rank.resize(n + 1, 0);
        parent.resize(n + 1);
        size.resize(n + 1);
        for (int i = 0; i <= n; i++) {
            parent[i] = i;
            size[i] = 1;
        }
    }

    int findUPar(int node) {
        if (node == parent[node])
            return node;
        return parent[node] = findUPar(parent[node]);
    }

    void unionByRank(int u, int v) {
        int ulp_u = findUPar(u);
        int ulp_v = findUPar(v);
        if (ulp_u == ulp_v) return;
        if (rank[ulp_u] < rank[ulp_v]) {
            parent[ulp_u] = ulp_v;
        }
        else if (rank[ulp_v] < rank[ulp_u]) {
            parent[ulp_v] = ulp_u;
        }
        else {
            parent[ulp_v] = ulp_u;
            rank[ulp_u]++;
        }
    }

    void unionBySize(int u, int v) {
        int ulp_u = findUPar(u);
        int ulp_v = findUPar(v);
        if (ulp_u == ulp_v) return;
        if (size[ulp_u] < size[ulp_v]) {
            parent[ulp_u] = ulp_v;
            size[ulp_v] += size[ulp_u];
        }
        else {
            parent[ulp_v] = ulp_u;
            size[ulp_u] += size[ulp_v];
        }
    }
};

// Global Constants
const int dx[4]{1, 0, -1, 0}, dy[4]{0, 1, 0, -1};  // for every grid problem!!
const int N=2e5+5;


void solve(){
    int n;
    cin >> n;
    vector<pii> arr(n);
    for(int i = 0; i < n; i++) {
        int a, b;
        cin >> a >> b;
        arr[i] = {a, b};
    }

    DisjointSet ds(2011);
    for(int i = 0; i < n; i++) {
        ds.unionBySize(arr[i].ff, arr[i].ss + 1005);
    }

    unordered_set<int> parents;
    for(int i = 1; i <= 2010; i++){
        if(ds.size[i] >= 2) {
            int parent = ds.findUPar(i);
            parents.insert(parent);
        }
    }
    int comps = parents.size();
    cout << comps - 1 << endl;


}


int32_t main(){
    fast

    int t = 1;
    // cin >> t;
    while(t--){


        solve();


    }
    return 0;
}