Submission #1865735

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

#define rep(i,n) for(int (i)=0;(i)<(int)(n);(i)++)
#define rept(i,n) for(int (i)=0;(i)<=(int)(n);(i)++)
#define reps(i,s,n) for(int (i)=(s);(i)<(int)(n);(i)++)
#define repst(i,s,n) for(int (i)=(s);(i)<=(int)(n);(i)++)
#define repr(i,n) for(int (i)=(n);(i)>=0;(i)--)
#define each(itr,v) for(auto (itr):(v))
#define all(c) (c).begin(),(c).end()
#define pb push_back
#define mp(x,y) make_pair((x),(y))
#define fi first
#define se second
#define chmin(x,y) x=min(x,y)
#define chmax(x,y) x=max(x,y)
#define ln "\n"
#define show(x) cout << #x << " = " << x ln
#define dbg(x) cout<<#x"="<<x ln

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vector<int> > mat;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

const int inf = (int)1e9;
const ll linf = (ll)1e18;
const int mod = (int)(1e9+7);
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
const int ddx[] = {0, 1, 1, 1, 0, -1, -1, -1};
const int ddy[] = {1, 1, 0, -1, -1, -1, 0, 1};

struct oreno_initializer {
	oreno_initializer() {
		cin.tie(0);
		ios::sync_with_stdio(0);
	}
} oreno_initializer;

// ━━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…
// .｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋.｡.:( ^ω^)・ﾟ＋
// ・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・‥…━━━☆・

int n, m, a, b;
// それぞれ 頂点0から行ける点全て、頂点n-1に行ける点全て
// 片方をソートして他方の値で二分探索すればok
vi mid, from;

int main() {
	cin >> n >> m;
	rep(i,m) {
		cin >> a >> b;
		a--, b--;
		if (a==0) mid.pb(b);
		else if (b==n-1) from.pb(a);
	}
	
	sort(all(from));
	each(itr,mid) {
		if (binary_search(all(from), itr)) {
			cout << "POSSIBLE" << ln;
			return 0;
		}
	}
	cout << "IMPOSSIBLE" << ln;
}

Submission Info

Judge Result