Cod sursa(job #1385278)

Utilizator taigi100Cazacu Robert taigi100 Data 11 martie 2015 20:39:18
Problema Stramosi Scor 80
Compilator cpp Status done
Runda Arhiva de probleme Marime 1.55 kb
/*
    Keep It Simple!
*/

#include <fstream>
#include <vector>
#include <list>
#include <stack>
#include <string>
#include <cmath>
#include <queue>
#include <vector>
#include <algorithm>
#include <iostream>

using namespace std;

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

#define ll long long
#define mp make_pair
#define fi first
#define se second
#define pb push_back

typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

const int kMaxN = 250005;

int lb[kMaxN],t[kMaxN];
int dp[20][kMaxN];
int n,m;

void ComputeLb()
{
    for(int i=2; i<=250000; ++i)
        lb[i] = lb[i/2] + 1;
}

void ReadInput()
{
    fin >> n >> m;
    for(int i=1; i<=n; ++i)
        fin >> t[i];
}

void ComputeDp()
{
    for(int j=1; j<=n; ++j)
        for(int i=0; 1<<i <= n; ++i)
            dp[i][j] = -1;

    for(int i=1; i<=n; ++i)
        dp[0][i] = t[i];

    for(int i=1; 1<<i <= n; ++i)
        for(int j=1; j<=n; ++j)
            if(dp[i-1][j] != -1)
            dp[i][j] = dp[i-1][dp[i-1][j]];
}

int Query(int P,int Q)
{
    int location = lb[P-1];
    Q = dp[location][Q];
    P -= 1<<location;
    while(P)
    {
        if(Q == -1 || !Q ) return 0;
        Q = t[Q];
        P--;
    }
    return Q;
}

void SolveQueries()
{
    int x,y;
    for(int i=1; i<=m; ++i)
    {
        fin >> x >> y;
        fout << Query(y,x) << '\n';
    }
}

void Solve()
{
    ComputeLb();
    ReadInput();
    ComputeDp();
    SolveQueries();
}

int main()
{
    Solve();
    return 0;
}