Submission #1726530

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Source Code Expand

// This file is a "Hello, world!" in C++ language by GCC for wandbox.
#include <iostream>
#include <cstdlib>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <cmath>

int main()
{
    int n,m;
    std::cin >> n;
    std::cin >> m; 
    std::vector<int> a,b;
    for(int i=0;i<m;i++){
        int x,y;
        std::cin >> x;
        std::cin >> y;
        a.push_back(x);
        b.push_back(y);
    }
    std::vector<int> start;
    std::vector<int> goal;
    for(int i=0;i<m;i++){
        if(a[i]==1)start.push_back(b[i]);
        if(b[i]==n)goal.push_back(a[i]);
    }
    if(start.size()==0||goal.size()==0){
        std::cout << "IMPOSSIBLE";
        return 0;
    }
    std::sort(start.begin(),start.end());
    std::sort(goal.begin(),goal.end());    
    int p=0;
    int q=0;
    int ssize = (int)start.size();
    int gsize = (int)goal.size();
        
    while(true){
        if(start[p]<goal[q])p=p+1;
        else if(start[p]>goal[q])q=q+1;
        else{
            std::cout << "POSSIBLE";
            return 0;
        }
        if(p+1>ssize||q+1>gsize){
            break;
        }
    }
    std::cout << "IMPOSSIBLE";
                
}

// GCC reference:
//   https://gcc.gnu.org/

// C++ language references:
//   https://msdn.microsoft.com/library/3bstk3k5.aspx
//   http://www.cplusplus.com/
//   https://isocpp.org/
//   http://www.open-std.org/jtc1/sc22/wg21/

// Boost libraries references:
//   http://www.boost.org/doc/

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