Finding digits in a number

This is a discussion on Finding digits in a number within the C Programming forums, part of the General Programming Boards category; I supposed to write a recursive code that finds the position of a particular digit in a number, starting from ...

  1. #1
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    Finding digits in a number

    I supposed to write a recursive code that finds the position of a particular digit in a number, starting from the right. Eg position(12345,3) = 3, position(123513, 3) = 1 ...

    My code goes like this
    Code:
    int position(int number, int digit) {
        if  ((number%10) == digit) return 1;
        return 1+ position(number/10, digit);
    }
    This works well and fine for all numbers except for cases when the digit is not found in the number. Eg position(12345, 8)
    I am supposed to return a 0 value, not print nothing when I use printf to print out the value.
    Eg position(1000, 4) = 0

    It looks easy but I am stumped by it. I'm sure some of you experts out there can help me with this.
    Thanks.

  2. #2
    Registered User quagsire's Avatar
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    This is not the best way to do it, but it works.
    Code:
    int search(int num, int sf)
    {
       char temp[100];
       sprintf(temp, "%d", num);
       char *pos = strrchr(temp, sf + '0');
       if (pos)
          return temp + strlen(temp) - pos;
    
       return 0;
    }
    To search from left to right, just change strrchr to strchr.

  3. #3
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    I was looking for a recursive solution along the lines of my solution.... I'm sure it can be done... it's just that I don't know how

    Pier.

  4. #4
    Registered User quagsire's Avatar
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    This is also not recursive, but works fine.
    Code:
    int position(int number, int digit)
    {
       int pos = 0;
       do
       {
          pos++;
          if ((number%10) == digit)
             return pos;
       }
       while (number/=10);
       return 0;
    }

  5. #5
    Me want cookie! Monster's Avatar
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    Here a recursive function:

    Code:
    int position(int number, int digit) {
       int ret = 0;
       if(number == 0) return 0;
       if((number%10) == digit) return 1;
       ret = position(number/10, digit);
       return (ret==0 ? 0 : 1+ret);
    }

  6. #6
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    Cool, Monster.... thanks a lot.

    Pier.
    Originally posted by Monster
    Here a recursive function:

    Code:
    int position(int number, int digit) {
       int ret = 0;
       if(number == 0) return 0;
       if((number%10) == digit) return 1;
       ret = position(number/10, digit);
       return (ret==0 ? 0 : 1+ret);
    }

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