Submission #1079570

#	Time	Username	Problem	Language	Result	Execution time	Memory
1079570		Lalic	Thousands Islands (IOI22_islands)	C++17	17.35 / 100	25 ms	6568 KiB

islands

#include "islands.h"
//~ #include <variant>
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define pb push_back
#define all(x) x.begin(), x.end()
#define allr(x) x.rbegin(), x.rend()
#define mp make_pair

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef complex<double> cd;

bool calc(int ver, int prev, vector<vector<pii>>& adj, vector<int>& cam){
	if((int)adj[ver].size()>=3-(ver==0)){
		int a=-1, va, b=-1, vb, c, d;
		
		for(auto u : adj[ver]){
			if(u.fi==prev) continue;
			if(a==-1){
				va=u.fi;
				a=u.se;
			}
			else{
				vb=u.fi;
				b=u.se;
				break;
			}
		}
		
		for(auto u : adj[va]){
			if(u.fi==ver){
				c=u.se;
				break;
			}
		}
		
		for(auto u : adj[vb]){
			if(u.fi==ver){
				d=u.se;
				break;
			}
		}
		
		vector<int> temp=cam;
		reverse(all(temp));
		
		cam.pb(a); cam.pb(c);
		cam.pb(b); cam.pb(d);
		cam.pb(c); cam.pb(a);
		cam.pb(d); cam.pb(b);
		
		for(auto u : temp) cam.pb(u);
		return 1;
	}
	
	for(auto [a, b]: adj[ver]){
		if(a==prev) continue;
		cam.pb(b);
		if(calc(a, ver, adj, cam)) return 1;
		cam.pop_back();
	}
	
	return 0;
}

variant<bool, vector<int>> find_journey(int N, int M, vector<int> U, vector<int> V) {
	vector<vector<pii>> adj(N);
	
	for(int i=0;i<M;i++) 
		adj[U[i]].pb({V[i], i});
	
	if(N==2){
		if((int)adj[0].size()>=2 && adj[1].size()>=1){
			int a=adj[0][0].se, b=adj[0][1].se, c=adj[1][0].se;
			return vector<int>({a, c, b, a, c, b});
		}
		return false;
	}
	
	vector<int> ans;
	if(calc(0, -1, adj, ans)) return ans;
	else return false;
}

Compilation message (stderr)

islands.cpp: In function 'bool calc(int, int, std::vector<std::vector<std::pair<int, int> > >&, std::vector<int>&)':
islands.cpp:35:22: warning: 'va' may be used uninitialized in this function [-Wmaybe-uninitialized]
   35 |   for(auto u : adj[va]){
      |                      ^
islands.cpp:42:22: warning: 'vb' may be used uninitialized in this function [-Wmaybe-uninitialized]
   42 |   for(auto u : adj[vb]){
      |                      ^

• Subtask 1: 5 / 5
• Subtask 2: 5 / 5
• Subtask 3: 7.35 / 21
• Subtask 4: 0 / 24
• Subtask 5: 0 / 45