Pagini recente » Cod sursa (job #2545180) | Cod sursa (job #2974227) | Cod sursa (job #748314) | Cod sursa (job #2438338) | Cod sursa (job #2817220)
#include <bits/stdc++.h>
using namespace std;
ifstream f("lca.in");
ofstream g("lca.out");
int n, number;
int m[20][100001], nivel[100001];
vector<int> graf[100001];
void read()
{
f>>n>>number;
for(int i = 2;i <= n;++i)
f>>m[0][i], graf[m[0][i]].push_back(i);
for(int j = 1;(1 << j) <= n;++j)
for(int i = 1;i <= n;++i)
m[j][i] = m[j - 1][m[j - 1][i]];
}
void dfs(int node, int lvl)
{
nivel[node] = lvl;
for(int vecin : graf[node])
dfs(vecin, lvl + 1);
}
int lca(int x, int y)
{
if(nivel[x] < nivel[y])
swap(x, y);
int logx, logy;
for(logx = 1;(1 << logx) <= nivel[x];++logx);
for(logy = 1;(1 << logy) <= nivel[y];++logy);
for(int k = logx;k >= 0;--k)
if(nivel[x] - (1 << k) >= nivel[y])
x = m[k][x];
if(x == y)
return x;
for(int k = logy;k >= 0;--k)
if(m[k][x] && m[k][x] != m[k][y])
x = m[k][x], y = m[k][y];
return m[0][x];
}
void solve()
{
dfs(1, 1);
int x, y;
for(int i = 1;i <= number;++i)
f>>x>>y, g<<lca(x, y)<<'\n';
}
int main()
{
read();
solve();
return 0;
}