CODEWITHSUNDEEP
c++functionrecursion
u.28292
u.28292

Reputation: 31

Recursive function to counting specific digit

I need to create a recursive function that counts the 2 and 6 from the number a user inputs.

For example if the user enters 26827 the count is 3.

It works with certain numbers and certain numbers it doesn't. Can someone please modify my function making sure its recursive and using very basic C++ language as I have used. Thank you! (I believe something is wrong with return type.) 

int count(int n) {
    static int count = 0; 
    if (n == 2 || n == 6) count++;
    if ((n % 10 == 2) || (n % 10 == 6)) {
        count++; 
        count(num / 10);
    }
    else return count;  
}

Upvotes: 0

Views: 1870

Answers (4)

Md. Mokammal Hossen Farnan
Md. Mokammal Hossen Farnan

Reputation: 445

If you want to make it with recursion , another procedure you can apply using string manipulation.

PseudoCode:

Function ( int n):
     1. Make n as a string. ( Convert Number to string)
     2. Collect the first character (char C) of the string and remove the character from the string.
     3. Make the main string again as a number n. ( Convert String to Number).
     4. Check the character C , which is number 2 or 6 or not, count it with a flag.
     5. Enter base case for which the recursion will stop.
     6. return the number n , inside the Function (n) for recursion.

Upvotes: 0

Brij Raj Kishore
Brij Raj Kishore

Reputation: 1705

int count(int n) {
    if(n <= 0) return 0;  // Base Condition
    int countDig = 0;       // Initalizing Count of digits 
    if(n % 10 == 2 || n % 10 == 6)  // Checking whether the LSB is 2 or 6
        countDig ++; // If it is then incrementing the countDig
    countDig += count(n / 10);  // Calling the recurive function by sending the number except its LSB
                        //And incrementing counter according to it
    return countDig;    // Returning the final count
}

you don't need to have a static value counter. It can be easily done as above. Please refer to comments given. Second the error in your code is you only calling the recursion if the LSB is 2 or 6. The recursion should be put outside the if condition in your code. Why are you using num variable. I think it should be n

Upvotes: 1

גלעד ברקן
גלעד ברקן

Reputation: 23955

One liner for fun.

int f(int n) {
  return n == 0 ? 0 : (n%10==2 || n%10==6) + f(n/10);
}

Upvotes: 2

vrtex
vrtex

Reputation: 165

You don't need statics This should work (note return c + count(n / 10) line. That's the main recursion here)

int count(int n)
{
    int c = 0;
    if(n % 10 == 2 || n % 10 == 6)
        c = 1;
    if(n < 10)
        return c;
    return c + count(n / 10);
}

Upvotes: 0

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