Drone Delivery Codechef

Problem Code: DRONEDEL

Contest :  LockDown Test 4.0 
Problem Link : https://www.codechef.com/LDT42020/problems/DRONEDEL


Solution 

#include<bits/stdc++.h>
using namespace  std ;
typedef long long  ll;
typedef pair<ll, ll> Pll;
#define F first
#define S second
#define MP make_pair
#define PB push_back
#define rad(X) cout << (X) << endl
#define ASH(X) cout << (X) << " "
#define debug(x) cout << #x << " " << x << endl;
#define debug2(x,y) cout << #x << " " << x << " " << #y << " " << y << endl;
#define FOR(I,A,B) for(ll I = (A); I <= (B); I++)
#define cir(I,B,A) for(ll I = (A); I >=(B); I--)
#define MS0(X) memset((X), 0, sizeof((X)))
#define MS1(X) memset((X), -1, sizeof((X)))
#define SORT(c) (sort(c.begin(),c.end()))
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#define GET_POS(c,x) (lower_bound(c.begin(),c.end(),x)-c.begin())
#define CASES int ___T; cin >> ___T; for(int cs=1;cs<=___T;cs++)
#define FAST()  ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
template<typename T>T gcd(T x, T y){if(y==0)return x;else return gcd(y,x%y);}
ll fx[] = {1, 1, 0, -1, -1, -1, 0, 1};
ll fy[] = {0, 1, 1, 1, 0, -1, -1, -1};
vector<ll>a,b,c;
map<ll,ll>m1,m2,m3;

/************************************************/

void Execute()
{
      ll n, nb=0, k, q, a, b, c, l, r, d, x, y, p, m, z;
      cin >> n >> l;
      ll ar[n+1];
      ll bb[n+1];
      c = 0;
      p = 0;
      m = 0;
      std::vector<ll> v,v1;
      ll mn = 1e9;


      FOR(i,1,n)
      {
        cin >> ar[i];
        v.PB(ar[i]);
        if(i>1)
        {
          x = ar[i]-ar[i-1];
          nb = gcd(x,nb);
          v1.PB(x);
        }

      }


       y = upper_bound(v.begin(),v.end(),l)-v.begin();
       z = lower_bound(v.begin(),v.end(),l)-v.begin();

       ll samne = v[y]-l;
       ll pichone = l-v[z];
       if(samne<0) samne=0;
       if(pichone<0) pichone =0;
       nb=gcd(nb,samne);
       nb = gcd(nb,pichone);

       std::cout << nb << '\n';

}

int32_t main()
{
  //  #ifndef ONLINE_JUDGE
    //freopen("input.txt", "r", stdin);
  //  #endif

    FAST();
  //  CASES
  //  {
        Execute();
    //}
}