Problem p02779 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
const int MOD = 1e9 + 7;

#define rep(i, b) for (i = 0; i < b; ++i)
#define repp(i, a, b) for (i = a; i < b; ++i)

int main() {
  ll num;
  bool flag = false;
  cin >> num;
  std::vector<bool> v(10010001, false);
  for (int i = 0; i < num; i++) {
    ll x;
    cin >> x;
    if (v[x]) {
      cout << "NO";
      flag = true;
      break;
    } else
      v[x] = true;
  }
  if (!flag)
    cout << "YES";
  return 0;
}
/*
         ,--"""",--.__,---[],-------._
       ,"   __,'            \         \--""""""==;-
     ," _,-"  "/---.___     \       ___\   ,-'',"
    /,-'      / ;. ,.--'-.__\  _,-"" ,| `,'   /
   /``""""-._/,-|:\       []\,' ```-/:;-. `. /
             `  ;:::      ||       /:,;  `-.\
                =.,'__,---||-.____',.=
                =(:\_     ||__    ):)=
               ,"::::`----||::`--':::"._
             ,':::::::::::||::::::::::::'.
    .__     ;:::.-.:::::__||___:::::.-.:::\     __,
       """-;:::( O )::::>_|| _<::::( O )::::-"""
   =======;:::::`-`:::::::||':::::::`-`:::::\=======
    ,--"";:::_____________||______________::::""----.          , ,
         ; ::`._(    |    |||     |   )_,'::::\_,,,,,,,,,,____/,'_,
       ,;    :::`--._|____[]|_____|_.-'::::::::::::::::::::::::);_
      ;/ /      :::::::::,||,:::::::::::::::::::::::::::::::::::/
     /; ``''''----------/,'/,__,,,,,____:::::::::::::::::::::,"
     ;/                :);/|_;| ,--.. . ```-.:::::::::::::_,"
    /;                :::):__,'//""\\. ,--.. \:::,:::::_,"
   ;/              :::::/ . . . . . . //""\\. \::":__,"
   ;/          :::::::,' . . . . . . . . . . .:`::\
   ';      :::::::__,'. ,--.. . .,--. . . . . .:`::`
   ';   __,..--'''-. . //""\\. .//""\\ . ,--.. :`:::`
   ;    /  \\ .//""\\ . . . . . . . . . //""\\. :`::`
   ;   /       . . . . . . . . . . . . . . . . .:`::`
   ;   (          . . . . . . . . . . . . . . . ;:::`
   ,:  ;,            . . . . . . . . . . . . . ;':::`
   ,:  ;,             . . . . . . . . . . . . .;`:::
   ,:   ;,             . . . . . . . . . . . . ;`::;`
    ,:  ;             . . . . . . . . . . . . ;':::;`
     :   ;             . . . . . . . . . . . ,':::;
      :   '.          . . . . . . . .. . . .,':::;`
       :    `.       . . . . . . . . . . . ;::::;`
        '.    `-.   . . . . . . . . . . ,-'::::;
          `:_    ``--..___________..--'':::::;'`
             `._::,.:,.:,:_ctr_:,:,.::,.:_;'`
________________`"\/"\/\/'""""`\/"\/""\/"____________________________

*/


Fixed submission:
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
const int MOD = 1e9 + 7;

#define rep(i, b) for (i = 0; i < b; ++i)
#define repp(i, a, b) for (i = a; i < b; ++i)

int main() {
  ll num;
  bool flag = false;
  cin >> num;
  std::vector<bool> v(1001001001, false);
  for (int i = 0; i < num; i++) {
    ll x;
    cin >> x;
    if (v[x]) {
      cout << "NO";
      flag = true;
      break;
    } else
      v[x] = true;
  }
  if (!flag)
    cout << "YES";
  return 0;
}
/*
         ,--"""",--.__,---[],-------._
       ,"   __,'            \         \--""""""==;-
     ," _,-"  "/---.___     \       ___\   ,-'',"
    /,-'      / ;. ,.--'-.__\  _,-"" ,| `,'   /
   /``""""-._/,-|:\       []\,' ```-/:;-. `. /
             `  ;:::      ||       /:,;  `-.\
                =.,'__,---||-.____',.=
                =(:\_     ||__    ):)=
               ,"::::`----||::`--':::"._
             ,':::::::::::||::::::::::::'.
    .__     ;:::.-.:::::__||___:::::.-.:::\     __,
       """-;:::( O )::::>_|| _<::::( O )::::-"""
   =======;:::::`-`:::::::||':::::::`-`:::::\=======
    ,--"";:::_____________||______________::::""----.          , ,
         ; ::`._(    |    |||     |   )_,'::::\_,,,,,,,,,,____/,'_,
       ,;    :::`--._|____[]|_____|_.-'::::::::::::::::::::::::);_
      ;/ /      :::::::::,||,:::::::::::::::::::::::::::::::::::/
     /; ``''''----------/,'/,__,,,,,____:::::::::::::::::::::,"
     ;/                :);/|_;| ,--.. . ```-.:::::::::::::_,"
    /;                :::):__,'//""\\. ,--.. \:::,:::::_,"
   ;/              :::::/ . . . . . . //""\\. \::":__,"
   ;/          :::::::,' . . . . . . . . . . .:`::\
   ';      :::::::__,'. ,--.. . .,--. . . . . .:`::`
   ';   __,..--'''-. . //""\\. .//""\\ . ,--.. :`:::`
   ;    /  \\ .//""\\ . . . . . . . . . //""\\. :`::`
   ;   /       . . . . . . . . . . . . . . . . .:`::`
   ;   (          . . . . . . . . . . . . . . . ;:::`
   ,:  ;,            . . . . . . . . . . . . . ;':::`
   ,:  ;,             . . . . . . . . . . . . .;`:::
   ,:   ;,             . . . . . . . . . . . . ;`::;`
    ,:  ;             . . . . . . . . . . . . ;':::;`
     :   ;             . . . . . . . . . . . ,':::;
      :   '.          . . . . . . . .. . . .,':::;`
       :    `.       . . . . . . . . . . . ;::::;`
        '.    `-.   . . . . . . . . . . ,-'::::;
          `:_    ``--..___________..--'':::::;'`
             `._::,.:,.:,:_ctr_:,:,.::,.:_;'`
________________`"\/"\/\/'""""`\/"\/""\/"____________________________

*/