Created
March 7, 2020 12:22
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#include<bits/stdc++.h> | |
#define ll unsigned long long int | |
#define mx 10005 | |
using namespace std; | |
vector <int> G[mx]; | |
int level[mx],parent[mx]; | |
int sparse_table[30][mx]; | |
void dfs(int val,int from,int lvl) | |
{ | |
level[val]=lvl; | |
parent[val]=from; | |
for(int i=0;i<G[val].size();i++) | |
{ | |
if(G[val][i]!=val) | |
dfs(G[val][i],val,lvl+1); | |
} | |
} | |
int find_par(int p,int pw) | |
{ | |
if(pw==0) | |
return sparse_table[pw][p]=parent[p]; | |
if(sparse_table[pw][p]!=-1) | |
return sparse_table[pw][p]; | |
int x; | |
x=find_par(p,pw-1); | |
return sparse_table[pw][p]=find_par(x,pw-1); | |
} | |
int lca_find(int p,int q) | |
{ | |
if(level[p]<level[q]) | |
swap(p,q); | |
for(int i=20;i>=0;i--) | |
{ | |
if(level[p]-(1<<i)>=level[q]) | |
p=find_par(p,i); | |
} | |
if(p==q) | |
return p; | |
for(int i=20;i>=0;i--) | |
{ | |
if(find_par(p,i)!=find_par(q,i)) | |
p=find_par(p,i),q=find_par(q,i); | |
} | |
return parent[p]; | |
} | |
int main() | |
{ | |
G[0].push_back(1); | |
G[1].push_back(2); | |
G[1].push_back(8); | |
G[2].push_back(3); | |
G[3].push_back(4); | |
G[4].push_back(5); | |
G[5].push_back(6); | |
G[6].push_back(14); | |
G[6].push_back(7); | |
G[8].push_back(9); | |
G[9].push_back(10); | |
G[10].push_back(11); | |
G[11].push_back(12); | |
G[11].push_back(15); | |
G[12].push_back(13); | |
G[12].push_back(16); | |
memset(sparse_table,-1,sizeof sparse_table); | |
dfs(0,0,0); | |
cout<<lca_find(13,7); | |
return 0; | |
} |
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