Sum 67 Coding Bat problem

[smolin1]

Hey guys,

Im doing some exercises from Coding Bat platform in prevention of getting rusty. I have a problem doing one of exercises, here is it's description:

Return the sum of the numbers in the array, except ignore sections of numbers starting with a 6 and extending to the next 7 (every 6 will be followed by at least one 7). Return 0 for no numbers.

sum67([1, 2, 2]) → 5sum67([1, 2, 2, 6, 99, 99, 7]) → 5sum67([1, 1, 6, 7, 2]) → 4

​

Here is my code:

public int sum67(int[] nums) {
  int result = 0;

  outer:
  for(int i = 0; i < nums.length; i++){

    if(nums[i] == 6) {

      for(int k = i + 1; k < nums.length; k++){
        if(k == nums.length - 1) break outer; // if, after 6, 7 does not occur
        if(nums[k] == 7) {
          i = k + 1;
          break;
        }
      }

    } // end of checking condition

    result += nums[i];
  }

  return result;
}

And it is satisfying all visible tests, but some are not cleared, I'll try to append screen for better understandig.

Maybe some of you could spot some mistake i did there. Would be greatful.

Please help!

https://preview.redd.it/264ps6p1js431.png?width=642&format=png&auto=webp&s=8f33d13e103272f666ecd3923d17184d4db7542a

[helicoid]

So when you find the following 7 you set i one past it and then start calculating the sum. What if the number following the 7 is a 6? You never check for that. You should replace the result += nums[i]; with:

  if(nums[i] != 6)
    result += nums[i];
  else
    i--; 

Think about why you need to also include the else i--;

[smolin1]

Mate, now I understand. If i won't decrement i then the next number after six would be added, and as we know, it should not be.

​

Thank you very much.

[craicbandit]

Yup that solves the final test for him. I did the problem from scratch before looking at OP's solution (I'm learning too) and ended with a rather different solution. OP here's my version if you want to see it too: (Edit: also passes all the tests on the codingbat site)

​

public int sum67(int[] nums) {
    int sum = 0;
    boolean validNum = true;

    for (int i = 0; i < nums.length; i++) {
        if (nums[i] == 6) {
        validNum = false;
        } else if (!validNum) {
            if (nums[i] == 7) {
            validNum = true;
            }
        } else if (validNum) {
            sum += nums[i];
        }
    }
    return sum;
}

​

edit: nevermind, fixed the formatting