Question

I am writing a program which has an output requirement for the number printed to not have a repeated integer in it

i.e. it would not print 122, 161, 998, etc
but it would print any other number such as 123, 345, 742..etc

how do i go about doing this? thanks!

Answer 1

A C-language compatible solution would be to convert the number to a string and keep a frequency count of the digits and return true if there are duplicates, e.g.:

int has_duplicate_digit(char * s) {
  char digit_count[10] = {0,0,0,0,0,0,0,0,0,0};
  for (int i=0; i<strlen(s); i++) {
    if ('0' <= s[i] && s[i] <= '9') {
      if (++digit_count[s[i]-'0'] > 1) return 1; // true
    }
  }
  return 0; // false
}

[Edit] You can also save a few bytes (and possibly some time) by using a bitset instead of an int array. For example:

#include <stdint.h>
int has_duplicate_digit2(char * s) {
  uint16_t digit_count = 0;
  for (int i=0; i<strlen(s); i++) {
    if ('0' <= s[i] && s[i] <= '9') {
      uint16_t bit = 1 << (s[i] - '0');
      if (digit_count & bit) return 1; // true
      digit_count |= bit;
    }
  }
  return 0; // false
}