Company Queries II

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

using namespace std;

const int MAXN = 200000;
const int LOG = 20;

vector<long long> tree[MAXN];
long long parent[MAXN][LOG];
long long depth[MAXN];
long long n, q;

void dfs(long long node, long long par) {
    parent[node][0] = par;
    for (long long i = 1; i < LOG; i++) {
        if (parent[node][i - 1] != -1) {
            parent[node][i] = parent[parent[node][i - 1]][i - 1];
        }
    }

    for (long long child : tree[node]) {
        if (child != par) {
            depth[child] = depth[node] + 1;
            dfs(child, node);
        }
    }
}

long long lca(long long a, long long b) {
    if (depth[a] < depth[b]) swap(a, b);

    for (long long i = LOG - 1; i >= 0; i--) {
        if (depth[parent[a][i]] >= depth[b]) {
            a = parent[a][i];
        }
    }

    if (a == b) return a;

    for (long long i = LOG - 1; i >= 0; i--) {
        if (parent[a][i] != parent[b][i]) {
            a = parent[a][i];
            b = parent[b][i];
        }
    }

    return parent[a][0];
}

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

    for (long long i = 0; i < MAXN; i++) {
        for (long long j = 0; j < LOG; j++) {
            parent[i][j] = -1;
        }
    }

    for (long long i = 2; i <= n; i++) {
        long long boss;
        cin >> boss;
        tree[boss].push_back(i);
    }

    depth[1] = 0;
    dfs(1, -1);

    for (long long i = 0; i < q; i++) {
        long long a, b;
        cin >> a >> b;
        cout << lca(a, b) << endl;
    }

    return 0;
}

Test 1

Verdict: WRONG ANSWER

Test 2

Verdict: WRONG ANSWER

Test 3

Verdict: WRONG ANSWER

Test 4

Verdict: WRONG ANSWER

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: RUNTIME ERROR

Test 7

Verdict: RUNTIME ERROR

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR

Test 11

Verdict: WRONG ANSWER

Test 12

Verdict: RUNTIME ERROR