Submission #420349

#	Time	Username	Problem	Language	Result	Execution time	Memory
420349		lakshith_	From Hacks to Snitches (BOI21_watchmen)	C++14	0 / 100	1234 ms	524292 KiB

watchmen

#include <bits/stdc++.h>

using namespace std;

//#define int long long 
#define what_is(a) cout << #a << " is " <<a << "\n"
#define checker(a) cout << "chekcer reached " << a << "\n"

inline void io(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
}

vector<vector<int>> adj(1000000,vector<int>());

struct node{
	int n,t,a;
};

void print(node n){
	cout << n.n << " " << n.t << " " << n.a << "\n";
}

void solve(){
	int n,m;
	cin >> n >> m;
	for(int i=0;i<m;i++){
		int u,v;
		cin >>u >> v;
		u--,v--;
		adj[u].push_back(v);
		adj[v].push_back(u);
	}
	int k,l;
	cin >> k;
	assert(k==1);
	cin >> l;
	vector<int> w;
	for(int i=0;i<l;i++){
		int a;
		cin >> a;
		a--;
		w.push_back(a);
	}
		
	int ans = -1;
	queue<node> q;
	q.push({0,0,0});
	while(!q.empty()){
		node u = q.front();
		//print(u);
		q.pop();
		if(u.n==n-1){
			ans = u.a;
			break;
		}
		for(int v:adj[u.n]){
			if(w[(u.t+1)%l]==v)continue;
			if(w[(u.t+1)%l]==u.n&&w[(u.t)%l]==v)continue;
			q.push({v,(u.t+1)%l,u.a+1});
		}
		if(w[(u.t+1)%l]!=u.n)
			q.push({u.n,(u.t+1)%l,u.a+1});
	}
	cout << (ans==-1?"impossible":to_string(ans)) << " \n";
}

signed main(){
	solve();
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 10
• Subtask 3: 0 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 25
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20