Cod sursa(job #1309852)

Utilizator thesvcoolmanLucian Bicsi thesvcoolman Data 6 ianuarie 2015 09:09:01
Problema Lowest Common Ancestor Scor 90
Compilator cpp Status done
Runda Arhiva educationala Marime 0.87 kb
#include<fstream>
#include<vector>

#define NMAX 102

using namespace std;

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

vector<int> PARENT;
vector<int> RANK;
int n, t;

int makeRank(int i) {
    if(i == 1) return 0;
    if(RANK[i]) return RANK[i];
    else RANK[i] = makeRank(PARENT[i]) + 1;
}

int lca (int a, int b) {
    while(RANK[a] > RANK[b]) {
        a = PARENT[a];
    }
    while(RANK[b] > RANK[a]) {
        b = PARENT[b];
    }
    while(b != a) {
        a = PARENT[a];
        b = PARENT[b];
    }

    return a;
}

int main() {
    fin>>n>>t;
    PARENT.resize(n+1, 0);
    RANK.resize(n+1, 0);

    for(int i=2; i<=n; i++) {
        fin>>PARENT[i];
        RANK[i] = RANK[PARENT[i]] + 1;
    }

    int a, b;
    for(int i=1; i<=t; ++i) {
        fin>>a>>b;
        fout<<lca(a, b)<<'\n';
    }

    return 0;
}