Cod sursa(job #1730273)

Utilizator cubaLuceafarul cuba Data 16 iulie 2016 17:58:57
Problema Lowest Common Ancestor Scor 0
Compilator cpp Status done
Runda Arhiva educationala Marime 1.44 kb
#include <bits/stdc++.h>
using namespace std;
ifstream f("lca.in");
ofstream g("lca.out");
const int NMAX = 100005;
int n , m, dp[23][NMAX], Niv[NMAX];
vector <int> Graf[NMAX];
inline void Read() {
    int x;
    f >> n >> m;
    for(int i = 2; i <= n ; i++) {
        f>> x;
        dp[0][i] = x;
        Graf[x].push_back(i);
    }
    for(int k = 1; (1<<k)<= n ; k++) {
        for(int i = 1; i <= n ; i++) {
            dp[k][i] = dp[k-1][dp[k-1][i]];
        }
    }
}
inline void Dfs(int nod, int nivel) {

    Niv[nod] = nivel;
    for(auto i: Graf[nod]) {
        Dfs(i, nivel+1);
    }
}
inline int Stramos(int x, int y) { ///returneaza al y-lea stramos al lui x

    int p = x;
    for(int i = 0; i <= 20 && y >= 0; i++)
    {
        if( y & (1<<i) ){
            p = dp[i][p];
            y = (1<<i);
        }
    }
    return p;
}
inline void Solve(int x, int y) {

    if(Niv[x] < Niv[y])
        swap(x,y);
    x = Stramos(x, Niv[x] - Niv[y]);
    if(x == y) {
        g<< x << "\n";
        return ;
    }
    for(int j = 20; j >= 0 ; j--) {

        if(dp[j][x] != dp[j][y]) {
            x = dp[j][x];
            y = dp[j][y];
        }
    }
    g<< Stramos(x,1) << "\n";

}
int main()
{
    int x, y;
    Read();
    Dfs(1,0);
    //g<< Stramos (7,1);
    for(int i = 1 ; i <= m; i++) {
        f>> x >> y;
        //g<< x << y << "\n";
        Solve(x,y);
    }
    return 0;
}