CODEWITHSUNDEEP
javarecursion
Jake
Jake

Reputation: 13

Recursive method to return number of zeroes

This is from an old test that I'm using to study. I need to write a recursive method that returns the number of zeroes on the int[] from position 0 and right. given int numberOfZeroes(int[] a, int right);

Upvotes: 1

Views: 2425

Answers (2)

Andrew Marshall
Andrew Marshall

Reputation: 96934

This assumes right < a.length

int numberOfZeroes(int[] a, int right) {
  if(right < 0) {  // We've gone through all indices
    return 0;  // So we don't want to recurse anymore
  } else if(a[right] == 0) {  // The current index has a zero
    return 1 + numberOfZeroes(a, right - 1); // Call the function, moving left one. Add one to the returned count since we found a zero
  } else {  // The current index does not have a zero
    return numberOfZeroes(a, right - 1); // Call the function, moving left one. We don't add anything since we didn't find a zero
  }
}

Upvotes: 1

David Nehme
David Nehme

Reputation: 21572

int numberOfZeroes(int[] a, int right) {
     if (right == 0) return 0;
     return numberOfZeros(a, right-1) + a[right] == 0 ? 0 : 1;
}

Do numberOfZeros(a, a.length) to get the number of zeros in the entire array.

Upvotes: 1

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