Pagini recente » Cod sursa (job #1146445) | Cod sursa (job #1303357) | Cod sursa (job #1536817) | Cod sursa (job #906299) | Cod sursa (job #2720779)
#include <bits/stdc++.h>
using namespace std;
ifstream f("lca.in");
ofstream g("lca.out");
int n, k, x, y, m[30][100005], nivel[100005];
vector<int> graf[100005];
void Read()
{
f>>n>>k;
for(int i = 2;i <= n;++i)
f>>x, m[0][i] = x, graf[x].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 nod, int lvl)
{
nivel[nod] = lvl;
for(auto it : graf[nod])
dfs(it, lvl + 1);
}
int lca(int x, int y)
{
if(nivel[x] < nivel[y])
swap(x, y);
int diff = nivel[x] - nivel[y];
for(int i = 0;(1 << i) <= diff;++i)
if(diff & (1 << i))
x = m[i][x];
if(x == y) return x;
for(int i = 30;i >= 0;--i)
if(m[i][x] && m[i][x] != m[i][y])
x = m[i][x], y = m[i][y];
return m[0][x];
}
void Solve()
{
dfs(1, 0);
for(int i = 1;i <= k;++i)
f>>x>>y, g<<lca(x, y)<<'\n';
}
int main()
{
Read();
Solve();
return 0;
}