Submission #1041488

#	Time	Username	Problem	Language	Result	Execution time	Memory
1041488		Alihan_8	Highway Tolls (IOI18_highway)	C++17	18 / 100	244 ms	262144 KiB

highway

#include "highway.h"

#include <bits/stdc++.h>

using namespace std;

#define all(x) x.begin(), x.end()
#define ar array
#define pb push_back
#define ln '\n'
//#define int long long

using i64 = long long;

template <class F, class _S>
bool chmin(F &u, const _S &v){
    bool flag = false;
    if ( u > v ){
        u = v; flag |= true;
    }
    return flag;
}

template <class F, class _S>
bool chmax(F &u, const _S &v){
    bool flag = false;
    if ( u < v ){
        u = v; flag |= true;
    }
    return flag;
}

void find_pair(int N, std::vector<int> U, std::vector<int> V, int A, int B) {
	int n = N, m = U.size();
	
	vector <vector<ar<int,2>>> adj(n);
	
	for ( int i = 0; i < m; i++ ){
		adj[U[i]].pb({V[i], i});
		adj[V[i]].pb({U[i], i});
	}
	
	vector <int> w(m);
	
	i64 C = ask(w);
	
	bool isSplitted = false;
	
	vector <int> blocked(m);
	
	ar <int,2> ans = {-1, -1};
	
	vector <int> s(n), f(n), cut(n);
	
	auto dfs = [&](auto dfs, int u, int p) -> void{
		s[u] = 1;
		f[u] = cut[u];
		
		for ( auto &[v, j]: adj[u] ){
			if ( v != p && !blocked[j] ){
				dfs(dfs, v, u);
				
				f[u] += f[v];
				s[u] += s[v];
			}
		}
	};
	
	auto get = [&](auto get, int u, int p, int des) -> int{
		for ( auto &[v, j]: adj[u] ){
			if ( v != p && !blocked[j] ){
				if ( s[v] >= des ){
					return get(get, v, u, des);
				}
			}
		}
		
		return u;
	};
	
	vector <int> tmp; // stores edges
	
	auto trav = [&](auto trav, int u, int p) -> void{
		for ( auto &[v, j]: adj[u] ){
			if ( v != p && !blocked[j] ){
				tmp.pb(j);
				
				trav(trav, v, u);
			}
		}
	};
	
	auto dec = [&](auto dec, int rt) -> void{
		dfs(dfs, rt, -1);
		
		int u = get(get, rt, -1, s[rt] / 2); // centroid
		
		dfs(dfs, u, -1);
		
		if ( s[u] == 1 ){
			swap(ans[0], ans[1]);
			
			ans[0] = u;
			
			return;
		}
		
		int nxt = -1, mx = -1, it = -1;
		
		for ( auto &[v, j]: adj[u] ){
			if ( blocked[j] ) continue;
			
			if ( chmax(mx, s[v]) ){
				nxt = v, it = j;
			}
		}
		
		//~ cout << "Cur centroid : " << u << ln;
		//~ cout << "   cut -> " << nxt << ln;
		
		assert(it != -1);
		
		blocked[it] = true;
		
		w[it] = 1;
		i64 cur = ask(w);
		w[it] = 0;
		
		if ( isSplitted ){
			if ( cur == C ){ // cost didn't change
				if ( f[nxt] > 0 ){
					dec(dec, nxt);
				} else dec(dec, u);
			} else{
				if ( f[nxt] == 0 ){
					cut[nxt] = 1;
					dec(dec, nxt);
				} else{
					cut[u] = 1;
					dec(dec, u);
				}
			}
		} else{
			if ( cur != C ){
				isSplitted = true;
				
				cut[u] = cut[nxt] = 1;
				
				dec(dec, u), dec(dec, nxt);
			} else{
				trav(trav, nxt, u);
				
				for ( auto &x: tmp ){
					w[x] = 1;
				}
				
				i64 T = ask(w);
				
				for ( auto &x: tmp ){
					w[x] = 0;
				} tmp.clear();
				
				if ( T != C ){
					dec(dec, nxt);
				} else{
					dec(dec, u);
				}
			}
		}
	};
	
	dec(dec, 0);
	
	//~ cout << "Answer : "; cout << ans[0] << " " << ans[1] << ln;
	
	answer(ans[0], ans[1]);
}

• Subtask 1: 5 / 5
• Subtask 2: 7 / 7
• Subtask 3: 6 / 6
• Subtask 4: 0 / 33
• Subtask 5: 0 / 18
• Subtask 6: 0 / 31