Company Queries II

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

typedef long long ll;


int main() {
    ll n,q;
    cin >> n >> q;

    ll a,b;
    ll array[n+1];
    ll adj[n+1];
    for(ll i = 0; i<n-1; i++) {
        cin >> a;
        array[i+2] = array[a]+1;
        adj[i+2] = a;
    }
    adj[1] = 1;

    ll ancestor[n+1][(ll)(ceil(log2(n)) + 1)] = {0};

    for(ll x = 1; x<=n; x++) {
        for(ll k = 0; k <= (ll)(ceil(log2(n))); k++) {
            if(k == 0) {
                ancestor[x][k] = adj[x];
            } else {
                ancestor[x][k] = ancestor[ancestor[x][k-1]][k-1];
            }
        }
    }


    ll outputs[q];
    for(ll i = 0; i<q; i++) {
        cin >> a >> b;
        ll k = 0;
        if(array[a] != array[b]) {
            if(array[a] < array[b]) swap(a,b);
            k = array[a] - array[b];
        }

        for(ll j = 0; (1LL << j) <= k; j++) {
            if(k & (1LL << j)) {
                a = ancestor[a][j];
            }
        }
        if(a == b) {
            outputs[i] = b;
            continue;
        }

        for(ll j = (ll)(ceil(log2(n))); j>=0; j--) {
            if(ancestor[a][j] != ancestor[b][j]) {
                a = ancestor[a][j];
                b = ancestor[b][j];
            }
        }
        outputs[i] = ancestor[b][0];
        
    }

    for(ll i = 0; i<q; i++) {
        cout << outputs[i] << " ";
    }

}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED