Submission #1462637

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Source Code Expand

#include <bits/stdc++.h>

#define x first
#define y second

#ifdef ONLINE_JUDGE
#define DEBUG(x)
#else
#define DEBUG(x) cerr << #x << ": " << x << endl;
#endif

using namespace std;

typedef long long ll;
typedef long double ld;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> ii;
typedef pair<ll,ll> pll;

const int mod=1000000000+7;

int addm(int& a,int b) {return (a+=b)<mod?a:a-=mod;}

template<class T,class U> bool smin(T& a,U b) {return a>b?(a=b,1):0;}
template<class T,class U> bool smax(T& a,U b) {return a<b?(a=b,1):0;}

bool a[200000],b[200000];
int N,M;

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);

	cin >> N >> M;
	for (int i=0;i<M;i++) {
		int u,v;cin >> u >> v;u--;v--;
		if (u==0) a[v]=1;
		if (v+1==N) b[u]=1;
	}
	for (int i=0;i<N;i++) if (a[i]&&b[i]) {
		cout << "POSSIBLE\n";
		return 0;
	}
	cout << "IMPOSSIBLE\n";
}

Submission Info

Judge Result