Pagini recente » Cod sursa (job #1581449) | Cod sursa (job #2797531) | Cod sursa (job #1134516) | Cod sursa (job #1873089) | Cod sursa (job #996467)
Cod sursa(job #996467)
#include <cstdio>
#include <algorithm>
#include <vector>
using namespace std;
const int MAX_N=100100;
const int MAX_LG=17;
int d[MAX_LG][MAX_N];
int lv[MAX_N];
vector<int> A[MAX_N];
int query(int x,int y) {
if(lv[x]>lv[y])
swap(x,y);
for(int i=MAX_LG;i>=0;i--) {
if((lv[x]-(1<<i))>=y) {
x=d[i][x];
}
}
if(x==y)
return x;
for(int i=MAX_LG;i>=0;i--) {
if(d[i][x] && d[i][x] != d[i][y]) {
x=d[i][x];
y=d[i][y];
}
}
return d[0][x];
}
void dfs(int nod,int lev) {
lv[nod]=lev;
for(vector<int>::iterator it=A[nod].begin();it!=A[nod].end();it++)
dfs(*it,lev+1);
}
int main() {
freopen("lca.in","r",stdin);
freopen("lca.out","w",stdout);
int n,m;
scanf("%d%d",&n,&m);
for(int i=2;i<=n;i++) {
scanf("%d",&d[0][i]);
A[d[0][i]].push_back(i);
for(int k=1;k<=MAX_LG;k++) {
if(i>(1<<k)) {
d[k][i]=d[k-1][d[k-1][i]];
}
}
}
dfs(1,1);
for(int i=1;i<=m;i++) {
int x,y;
printf("%d\n",query(x,y));
}
return 0;
}