Cod sursa(job #3277553)

Utilizator PetruApostolApostol Mihnea Petru PetruApostol Data 16 februarie 2025 17:34:11
Problema Lowest Common Ancestor Scor 10
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.34 kb
#include <fstream>
#include <vector>
using namespace std;

ifstream cin("lca.in");
ofstream cout("lca.out");

int mar[100001];
int par[100001];
int heavy[100001];
int tp[100001];
int nr[100001];
int adan[100001];
int cnt;
vector<int> v[100001];

void dfs(int tata,int nod){
    mar[nod]=1;
    for(auto it:v[nod]){
        if(it==tata) continue;
        adan[it]=adan[nod]+1;
        par[it]=nod;
        dfs(nod,it);
        mar[nod]+=mar[it];

        if(mar[it]>mar[heavy[nod]]) heavy[nod]=it;
    }
}

void dfs1(int tata,int nod,int top){

    nr[nod]=cnt;cnt++;
    tp[nod]=top;
    if(!heavy[nod]) return;
    dfs1(nod,heavy[nod],top);
    for(auto it:v[nod]){

        if(it==tata || it==heavy[nod]) continue;
        dfs1(nod,it,it);
    }
}

int lca(int a,int b){
    if(a>b) swap(a,b);
    while(tp[a]!=tp[b]){
        if(adan[a]<=adan[b]) b=par[tp[b]];
        else a=par[tp[a]];
    }
    printf("\n");
    if(adan[a]<adan[b]) return a;
    return b;
}

int main()
{
    int n,m,i,a,b;
    cin>>n>>m;
    for(i=2;i<=n;i++){
        cin>>a;

        v[a].push_back(i);
    }
    par[1]=1;
    dfs(1,1);
    dfs1(1,1,1);
    for(i=1;i<=n;i++){
        printf("%d ",adan[i]);
    }printf("\n");
    for(i=1;i<=m;i++){
        cin>>a>>b;
        cout<<lca(a,b)<<"\n";
    }
    return 0;
}