Cod sursa(job #950893)

Utilizator SRaduRadu Szasz SRadu Data 18 mai 2013 16:56:13
Problema Stramosi Scor 100
Compilator cpp Status done
Runda Arhiva de probleme Marime 0.76 kb
#include <fstream>

using namespace std;

const int MAX = 250005;
const int LG_MAX = 19;

int N, M;
int dp[LG_MAX][MAX];

void preprocess() {
    for(int i = 1, step = 2; step <= N; i++, step <<= 1) {
        for(int j = 1; j <= N; j++) 
            dp[i][j] = dp[i - 1][ dp[i - 1][j] ];
    }
}

inline int getAncestor(int guy, int ancestor) {
    for(int i = 0; (1 << i) <= ancestor; i++) {
        if((1 << i) & ancestor)
            guy = dp[i][guy];
    } return guy;
}

int main() {
    ifstream in("stramosi.in"); ofstream out("stramosi.out"); 
    in >> N >> M;
    for(int i = 1; i <= N; i++) 
        in >> dp[0][i];
    preprocess();
    for(int i = 1, X, Y; i <= M; i++) {
        in >> X >> Y;
        out << getAncestor(X, Y) << "\n";
    } in.close(); out.close();
}