Pagini recente » Cod sursa (job #2710575) | Cod sursa (job #2811574) | Cod sursa (job #524530) | Cod sursa (job #1082415) | Cod sursa (job #1914616)
#include <bits/stdc++.h>
#define NMAX 100005
using namespace std;
ifstream fin("lca.in");
ofstream fout("lca.out");
int L[NMAX],Chain[NMAX],H[NMAX],P[NMAX],chains = 0;
vector < int > G[NMAX];
void DFS(const int &nod){
int OC = 0;
for(auto const &it : G[nod]){
L[it] = L[nod] + 1;
if(OC == 1){
Chain[it] = ++chains;
P[Chain[it]] = nod;
} else{
OC = 1;
Chain[it] = Chain[nod];
}
DFS(it);
}
}
int LCA(int &x,int &y){
while(Chain[x] != Chain[y]){
if(L[P[Chain[x]]] > L[P[Chain[y]]])
x = P[Chain[x]];
else
y = P[Chain[y]];
}
if(L[x] < L[y])
return x;
return y;
}
int main()
{
ios :: sync_with_stdio(false);
int n,m,x,y;
fin >> n >> m;
for(int i = 2; i <= n; i++){
fin >> x;
G[x].push_back(i);
}
L[1] = 1;
DFS(1);
P[Chain[1]] = 0;
for(int i = 1; i <= m; i++){
fin >> x >> y;
fout << LCA(x,y) << "\n";
}
return 0;
}