C++ Program to check if a given number is Lucky (all digits are different)

Given with a number and the task is to check whether the input number is a lucky number or not and display the result.

What is a Lucky Number

Lucky number is the number whose each and every digit is different and if at least one digit is repeating than the number will not be considered as a lucky number.


Input-: n = 1234
Output-: it is a lucky number
Explanation-: As there is no repeating digit in a number n so it is a lucky number
Input-: n = 3434
Output-: it is not a lucky number
Explanation-: In the given number n, 3 and 4 are repeating twice so it is not a lucky number

Approach we are using in the given program is as follows

  • Input the number n from the user to check whether it’s a lucky number or not
  • Traverse the entire digit till the size of a number
  • Mark the digit visited on every visit and check whether it is already found or not
  • Display whether the given number is a lucky number or not


Step1-> declare function to check whether a given number is lucky or not
   bool check_lucky(int size)
   declare bool arr[10]
   Loop For int i=0 and i<10 and i++
      Set arr[i] = false
   Loop While(size > 0)
      declare int digit = size % 10
      IF (arr[digit])
         return false
      set arr[digit] = true
      Set size = size/10
   return true
Step 2-> In main()
   Declare int arr[] = {0,34,2345,1249,1232}
   calculate int size = sizeof(arr)/sizeof(arr[0])
   Loop For int i=0 and i<size and i++
      print  is Lucky : print is not Lucky


using namespace std;
//return true if a number if lucky.
bool check_lucky(int size) {
    bool arr[10];
    for (int i=0; i<10; i++)
        arr[i] = false;
    while (size > 0) {
    int digit = size % 10;
      if (arr[digit])
           return false;
        arr[digit] = true;
        size = size/10;
    return true;
int main() {
    int arr[] = {0,34,2345,1249,1232};
    int size = sizeof(arr)/sizeof(arr[0]);
    for (int i=0; i<size; i++)
        check_lucky(arr[i])? cout << arr[i] << " is Lucky \n": cout << arr[i] << " is not Lucky \n";
    return 0;


19 is Lucky
34 is Lucky
2345 is Lucky
1249 is Lucky
1232 is not Lucky

Updated on: 20-Nov-2019


Kickstart Your Career

Get certified by completing the course

Get Started