Submission #2551106

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Source Code Expand

#include<bits/stdc++.h>
typedef long long ll;
typedef unsigned long long ull;
using namespace std;
#define pb push_back
int dy[]={0, 0, 1, -1, 1, 1, -1, -1};
int dx[]={1, -1, 0, 0, 1, -1, -1, 1};

#define FOR(i,a,b) for (int i=(a);i<(b);i++)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n) for (int i=0;i<(n);i++)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define mp make_pair
#define fi first
#define sc second
ll n,m;
vector<ll> G[300000];
bool used[300000];
bool dfs(ll i,ll j) {
	if(i == n - 1) {
		return true;
	}
	if(j >= 2) 
		return false;

	bool ret = false;
	REP(k,G[i].size()) {
		if(!used[G[i][k]]){
			used[G[i][k]] = true;
			ret |= dfs(G[i][k],j + 1);
		}
	}
	return ret;
}
int main(){
	cin >> n >> m;
	REP(i,m) {
		ll a,b;
		cin >> a >> b;
		a--;b--;
		G[a].pb(b);
		G[b].pb(a);
	}
	if(dfs(0,0)) {
		cout << "POSSIBLE" << endl;
	}else {
		cout <<"IMPOSSIBLE" << endl;
	}

	return 0;
}

Submission Info

Judge Result