tree/lowestcommonancestor.cpp

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• Last update: 2020-10-27 19:32:25+09:00

Required by

• Auxiliary Tree (tree/auxiliarytree.cpp)

Verified with

• test/aoj/0439.test.cpp
• test/aoj/2270.test.cpp
• test/aoj/GRL_5_C.test.cpp
• test/yosupo/lca.test.cpp
• test/yukicoder/3407.test.cpp
• test/yukicoder/4852.test.cpp

Code

#ifndef call_from_test
#include<bits/stdc++.h>
using namespace std;
#endif
//BEGIN CUT HERE
struct LowestCommonAncestor{
  int h;
  vector< vector<int> > G,par;
  vector<int> dep;
  LowestCommonAncestor(int n):G(n),dep(n){
    h=1;
    while((1<<h)<=n) h++;
    par.assign(h,vector<int>(n,-1));
  }

  void add_edge(int u,int v){
    G[u].emplace_back(v);
    G[v].emplace_back(u);
  }

  void dfs(int v,int p,int d){
    par[0][v]=p;
    dep[v]=d;
    for(int u:G[v])
      if(u!=p) dfs(u,v,d+1);
  }

  void build(int r=0){
    int n=G.size();
    dfs(r,-1,0);
    for(int k=0;k+1<h;k++)
      for(int v=0;v<n;v++)
        if(~par[k][v])
          par[k+1][v]=par[k][par[k][v]];
  }

  int lca(int u,int v){
    if(dep[u]>dep[v]) swap(u,v);
    for(int k=0;k<h;k++)
      if((dep[v]-dep[u])>>k&1)
        v=par[k][v];

    if(u==v) return u;

    for(int k=h-1;k>=0;k--)
      if(par[k][u]!=par[k][v])
        u=par[k][u],v=par[k][v];

    return par[0][u];
  }

  int distance(int u,int v){
    return dep[u]+dep[v]-dep[lca(u,v)]*2;
  }
};
//END CUT HERE
#ifndef call_from_test
signed main(){
  return 0;
}
#endif

#line 1 "tree/lowestcommonancestor.cpp"

#include<bits/stdc++.h>
using namespace std;
#endif
//BEGIN CUT HERE
struct LowestCommonAncestor{
  int h;
  vector< vector<int> > G,par;
  vector<int> dep;
  LowestCommonAncestor(int n):G(n),dep(n){
    h=1;
    while((1<<h)<=n) h++;
    par.assign(h,vector<int>(n,-1));
  }

  void add_edge(int u,int v){
    G[u].emplace_back(v);
    G[v].emplace_back(u);
  }

  void dfs(int v,int p,int d){
    par[0][v]=p;
    dep[v]=d;
    for(int u:G[v])
      if(u!=p) dfs(u,v,d+1);
  }

  void build(int r=0){
    int n=G.size();
    dfs(r,-1,0);
    for(int k=0;k+1<h;k++)
      for(int v=0;v<n;v++)
        if(~par[k][v])
          par[k+1][v]=par[k][par[k][v]];
  }

  int lca(int u,int v){
    if(dep[u]>dep[v]) swap(u,v);
    for(int k=0;k<h;k++)
      if((dep[v]-dep[u])>>k&1)
        v=par[k][v];

    if(u==v) return u;

    for(int k=h-1;k>=0;k--)
      if(par[k][u]!=par[k][v])
        u=par[k][u],v=par[k][v];

    return par[0][u];
  }

  int distance(int u,int v){
    return dep[u]+dep[v]-dep[lca(u,v)]*2;
  }
};
//END CUT HERE
#ifndef call_from_test
signed main(){
  return 0;
}
#endif

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