test/yosupo/Tree/LCA_yosupo_2.test.cpp

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Last update: 2024-06-26 10:40:27+07:00
Problem: https://judge.yosupo.jp/problem/lca

Depends on

Code

#define PROBLEM "https://judge.yosupo.jp/problem/lca"
#include "Misc/marco.hpp"
#include "Misc/debug.hpp"
const int INF=1e9;
const ll INFI=1e15;
//----------Author: Nguyen Ho Nam,UIT, Saigon-----------------
#define sz(a) ((int) (a).size())
#include "DS/Sparse_table.hpp"
#include "tree/LCA_kactl.hpp"

int main() {
    int n,q,u,v,x; cin>>n>>q;
    vvc<int>g(n);
    For(i,1,n){
        cin>>x;
        g[i].push_back(x);
        g[x].push_back(i);
    }
    LCA lca(g);
    while(q--){
        cin>>u>>v;
        cout<<lca.lca(u,v)<<'\n';
    }
    return 0;
}

#line 1 "test/yosupo/Tree/LCA_yosupo_2.test.cpp"
#define PROBLEM "https://judge.yosupo.jp/problem/lca"
#line 2 "Misc/marco.hpp"
// Judges with GCC >= 12 only needs Ofast
// #pragma GCC optimize("O3,no-stack-protector,fast-math,unroll-loops,tree-vectorize")
// MLE optimization
// #pragma GCC optimize("conserve-stack")
// Old judges
// #pragma GCC target("sse4.2,popcnt,lzcnt,abm,mmx,fma,bmi,bmi2")
// New judges. Test with assert(__builtin_cpu_supports("avx2"));
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma,tune=native")
// Atcoder
// #pragma GCC target("avx2,popcnt,lzcnt,abm,bmi,bmi2,fma")
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update> ods;
- insert(x),erase(x)
- find_by_order(k): return iterator to the k-th smallest element
- order_of_key(x): the number of elements that are strictly smaller
*/
#include<bits/stdc++.h>
using namespace std;

using ld = long double;
using ll = long long;
using u32 = unsigned int;
using u64 = unsigned long long;
using i128 = __int128;
using u128 = unsigned __int128;
using f128 = __float128;
 
 
#define pii pair<int,int>
#define pll pair<ll,ll>
 
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(),(x).rend()
#define ars(x) (x),(x+n)
 
#define TIME  (1.0 * clock() / CLOCKS_PER_SEC)
 
#define For(i,a,b) for (int i=(a); i<(b); i++)
#define rep(i,a) For(i,0,a)
#define rev(i,a,b) for (int i=(a); i>(b); i--)
#define FOR(i,a,b) for (int i=(a); i<=(b); i++)
#define REP(i,a) FOR(i,1,a)
#define REV(i,a,b) for (int i=(a); i>=(b); i--)
 
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fi first
#define se second
#define FT ios_base::sync_with_stdio(false); cin.tie(nullptr);
 
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

using vi=vector<int>;
using vll = vector<ll>;
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vector<vc<T>>;
template <class T>
using vvvc = vector<vvc<T>>;
template <class T>
using vvvvc = vector<vvvc<T>>;
template <class T>
using vvvvvc = vector<vvvvc<T>>;
template <class T>
using pq = priority_queue<T>;
template <class T>
using pqg = priority_queue<T, vector<T>, greater<T>>;
 
#define vv(type, name, h, ...) \
  vector<vector<type>> name(h, vector<type>(__VA_ARGS__))
#define vvv(type, name, h, w, ...)   \
  vector<vector<vector<type>>> name( \
      h, vector<vector<type>>(w, vector<type>(__VA_ARGS__)))
#define vvvv(type, name, a, b, c, ...)       \
  vector<vector<vector<vector<type>>>> name( \
      a, vector<vector<vector<type>>>(       \
             b, vector<vector<type>>(c, vector<type>(__VA_ARGS__))))
 
//template <class T>
//using ods =
//   tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
 
template <typename T> bool chkmin(T &x,T y){return x>y?x=y,1:0;}
template <typename T> bool chkmax(T &x,T y){return x<y?x=y,1:0;}
 
template<class T> using pq = priority_queue<T>;
template<class T> using pqg = priority_queue<T, vector<T>, greater<T>>;
#line 1 "Misc/debug.hpp"
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ", "; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? ", " : ""), __print(i); cerr << "}";}
template<>
void __print(const vector<bool> &x) {int f = 0; cerr << '{'; for (size_t i = 0; i < x.size(); ++i) cerr << (f++ ? ", " : ""), __print(x[i]); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}

void dbg_out() { cerr << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { __print(H); if (sizeof...(T)) cerr << ", "; dbg_out(T...); }
#define dbg(...) cerr << "[" << #__VA_ARGS__ << "]:"; dbg_out(__VA_ARGS__);
#line 4 "test/yosupo/Tree/LCA_yosupo_2.test.cpp"
const int INF=1e9;
const ll INFI=1e15;
//----------Author: Nguyen Ho Nam,UIT, Saigon-----------------
#define sz(a) ((int) (a).size())
#line 2 "DS/Sparse_table.hpp"

template<class T>
struct sparsetable {
	vector<vector<T>> jmp;
	sparsetable(const vector<T>& V) : jmp(1, V) {
		for (int pw = 1, k = 1; pw * 2 <= V.size(); pw *= 2, ++k) {
			jmp.emplace_back(V.size() - pw * 2 + 1);
			rep(j,jmp[k].size())
				jmp[k][j] = min(jmp[k - 1][j], jmp[k - 1][j + pw]);
		}
	}
	T query(int a, int b) {
		assert(a < b); // or return inf if a == b
		int dep = 31 - __builtin_clz(b - a);
		return min(jmp[dep][a], jmp[dep][b - (1 << dep)]);
	}
};
#line 3 "tree/LCA_kactl.hpp"
struct LCA {
	int T = 0;
	vi time, path, ret,depth;
	sparsetable<int> rmq;

	LCA(vector<vi>& C) : time(sz(C)), rmq((dfs(C,0,-1), ret)) {}
	void dfs(vector<vi>& C, int v, int par) {
		time[v] = T++;
		for (int y : C[v]) if (y != par) {
			path.push_back(v), ret.push_back(time[v]);
			dfs(C, y, v);
		}
	}

	int lca(int a, int b) {
		if (a == b) return a;
		tie(a, b) = minmax(time[a], time[b]);
		return path[rmq.query(a, b)];
	}
	int dist(int a,int b){return depth[a] + depth[b] - 2*depth[lca(a,b)];}
};
#line 10 "test/yosupo/Tree/LCA_yosupo_2.test.cpp"

int main() {
    int n,q,u,v,x; cin>>n>>q;
    vvc<int>g(n);
    For(i,1,n){
        cin>>x;
        g[i].push_back(x);
        g[x].push_back(i);
    }
    LCA lca(g);
    while(q--){
        cin>>u>>v;
        cout<<lca.lca(u,v)<<'\n';
    }
    return 0;
}