Submission #2551586

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Source Code Expand

#include <bits/stdc++.h>
#define rep(i,j,k) for(ll i=(ll)j;i<(ll)k;i++)
#define itrep(i,x) for(auto i=(x).begin(); i!=(x).end();i++)
#define Sort(x) sort((x).begin(),(x).end())
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define vec vector
#define INF INT_MAX
#define INFL 1e18
#define MOD 1000000007
#define pb push_back
#define MP make_pair
#define PI 3.1415926535
typedef long long int ll;
typedef std::pair<int,int> P;
int D=1;
int dx[4]={0,1,0,-1},dy[4]={-1,0,1,0};

using namespace std;

int main(){
    int n,m;
    cin>>n>>m;
    vec<P> v(n);
    rep(i,0,n)v[i].fi=v[i].se=0;
    rep(i,0,m){
        int a,b;
        cin>>a>>b;
        if(a==1)v[b-1].fi++;
        if(b==n)v[a-1].se++;
    }
    
    rep(i,0,n){
        if(v[i].fi&&v[i].se){
            cout<<"POSSIBLE"<<endl;
            return 0;
        }
    }
    cout<<"IMPOSSIBLE"<<endl;
    return 0;
}

Submission Info

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