Problem p03645 (C++)

Buggy submission (status: Time Limit Exceeded):

#include <algorithm>
#include <fstream>
#include <functional>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <stack>
#include <stdlib.h>
#include <string>
#include <sys/timeb.h>
#include <vector>

using namespace std;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define reprrev(i, a, b) for (int i = (int)(b)-1; i >= (int)(a); i--)
#define reprev(i, n) reprrev(i, 0, n)
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define mp make_pair
#define mt make_tuple
#define INF 1050000000
#define INFL 1100000000000000000LL
#define EPS (1e-10)
#define MOD 1000000007
#define PI 3.1415926536
#define RMAX 4294967295

typedef long long ll;
typedef pair<int, int> Pi;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<Pi> vPi;
typedef vector<vector<int>> vvi;
typedef vector<vector<bool>> vvb;
typedef vector<vector<ll>> vvll;
typedef vector<vector<char>> vvc;
typedef vector<vector<string>> vvs;
typedef vector<vector<double>> vvd;
typedef vector<vector<Pi>> vvPi;
typedef priority_queue<int, vector<int>, greater<int>> pqli;
typedef priority_queue<ll, vector<ll>, greater<ll>> pqlll;
typedef priority_queue<Pi, vector<Pi>, greater<Pi>> pqlP;
struct Edge {
  int from, to, cost;
  bool operator<(Edge e) { return cost < e.cost; }
};
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
template <class T> using vec = vector<T>;
template <class T> using pql = priority_queue<T, vector<T>, greater<T>>;
string debug_show(Pi a) {
  return "(" + to_string(a.first) + "," + to_string(a.second) + ")";
}

template <class T> struct augEdge {
  T from, to;
  int cost;
  bool operator<(augEdge e) { return cost < e.cost; }
  bool operator>(augEdge e) { return cost > e.cost; }
};
template <class T> using augGraph = vector<augEdge<T>>;

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

  int n, m;
  cin >> n >> m;
  int a, b;
  vPi t;
  vi x, y;
  rep(i, m) {
    cin >> a >> b;
    // t.push_back(mp(a, b));
    if (a == 1) {
      x.push_back(b);
    }
    if (b == n) {
      y.push_back(a);
    }
  }
  sort(all(x));
  sort(all(y));
  rep(i, x.size()) {
    rep(j, y.size()) {
      if (x[i] == y[j]) {
        cout << "POSSIBLE" << endl;
        return 0;
      }
    }
  }
  // sort(all(t));
  /*
  rep(i, m) {
          if (t[i].first == 1) {
                  repr(j, i, m) {
                          if (t[i].second == t[j].first && t[j].second == n) {
                                  cout << "POSSIBLE" << endl;
                                  return 0;
                          }
                  }
          }
  }
  //*/
  cout << "IMPOSSIBLE" << endl;
  return 0;
}


Fixed submission:

#include <algorithm>
#include <fstream>
#include <functional>
#include <iostream>
#include <map>
#include <math.h>
#include <queue>
#include <stack>
#include <stdlib.h>
#include <string>
#include <sys/timeb.h>
#include <vector>

using namespace std;

#define repr(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repr(i, 0, n)
#define reprrev(i, a, b) for (int i = (int)(b)-1; i >= (int)(a); i--)
#define reprev(i, n) reprrev(i, 0, n)
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define mp make_pair
#define mt make_tuple
#define INF 1050000000
#define INFL 1100000000000000000LL
#define EPS (1e-10)
#define MOD 1000000007
#define PI 3.1415926536
#define RMAX 4294967295

typedef long long ll;
typedef pair<int, int> Pi;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<bool> vb;
typedef vector<char> vc;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<Pi> vPi;
typedef vector<vector<int>> vvi;
typedef vector<vector<bool>> vvb;
typedef vector<vector<ll>> vvll;
typedef vector<vector<char>> vvc;
typedef vector<vector<string>> vvs;
typedef vector<vector<double>> vvd;
typedef vector<vector<Pi>> vvPi;
typedef priority_queue<int, vector<int>, greater<int>> pqli;
typedef priority_queue<ll, vector<ll>, greater<ll>> pqlll;
typedef priority_queue<Pi, vector<Pi>, greater<Pi>> pqlP;
struct Edge {
  int from, to, cost;
  bool operator<(Edge e) { return cost < e.cost; }
};
typedef vector<Edge> Edges;
typedef vector<Edges> Graph;
template <class T> using vec = vector<T>;
template <class T> using pql = priority_queue<T, vector<T>, greater<T>>;
string debug_show(Pi a) {
  return "(" + to_string(a.first) + "," + to_string(a.second) + ")";
}

template <class T> struct augEdge {
  T from, to;
  int cost;
  bool operator<(augEdge e) { return cost < e.cost; }
  bool operator>(augEdge e) { return cost > e.cost; }
};
template <class T> using augGraph = vector<augEdge<T>>;

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

  int n, m;
  cin >> n >> m;
  int a, b;
  vPi t;
  vi x, y;
  rep(i, m) {
    cin >> a >> b;
    // t.push_back(mp(a, b));
    if (a == 1) {
      x.push_back(b);
    }
    if (b == n) {
      y.push_back(a);
    }
  }
  sort(all(x));
  sort(all(y));
  rep(i, x.size()) {
    if (binary_search(all(y), x[i])) {
      cout << "POSSIBLE" << endl;
      return 0;
    }
  }
  // sort(all(t));
  /*
  rep(i, m) {
          if (t[i].first == 1) {
                  repr(j, i, m) {
                          if (t[i].second == t[j].first && t[j].second == n) {
                                  cout << "POSSIBLE" << endl;
                                  return 0;
                          }
                  }
          }
  }
  //*/
  cout << "IMPOSSIBLE" << endl;
  return 0;
}