Cod sursa(job #2648081)

Utilizator BogdanRazvanBogdan Razvan BogdanRazvan Data 8 septembrie 2020 16:30:10
Problema Stramosi Scor 0
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 1.21 kb
#include <bits/stdc++.h>

using namespace std;

ifstream fin ("stramosi.in");
ofstream fout ("stramosi.out");

void usain_bolt()
{
    ios::sync_with_stdio(false);
    fin.tie(0);
}

const int N = 250000 + 5;

int dad[20][N], parent[N];

void binary_lift(int n)
{
    for(int i = 1; i <= n; ++i) {
        for(int j = 0; j <= 18; ++j) {
            dad[i][j] = -1;
        }
    }
    for(int i = 1; i <= n; ++i) {
        if(parent[i] != 0) dad[i][0] = parent[i];
    }
    for(int j = 1; (1 << j) <= n; ++j) {
        for(int i = 1; i <= n; ++i) {
            if(dad[i][j - 1] != -1) {
                dad[i][j] = dad[dad[i][j - 1]][j - 1];
            }
        }
    }
}

int find_asc(int k, int lvl)
{
    for(int i = 18; i >= 0 && lvl > 0; --i) {
        if(lvl >= (1 << i) && dad[k][i] != -1) k = dad[k][i], lvl -= (1 << i);
    }
    if(lvl > 0) return 0;
    return k;
}

int main()
{
    usain_bolt();

    int n, q;

    fin >> n >> q;
    for(int i = 1; i <= n; ++i) {
        fin >> parent[i];
    }
    binary_lift(n);
    for(int i = 1; i <= q; ++i) {
        int x, y;

        fin >> x >> y;
        fout << find_asc(x, y) << "\n";
    }
    return 0;
}