Array problem: I have never been so lost.

[TinyTertle]

This problem is actually written in Java, but it should still be readable by anyone who has never worked with Java. The problem is as follows:

Say that a "clump" in an array is a series of 2 or more adjacent elements of the same value. Return the number of clumps in the given array.

countClumps({1, 2, 2, 3, 4, 4}) → 2
countClumps({1, 1, 2, 1, 1}) → 2
countClumps({1, 1, 1, 1, 1}) → 1

My solution is as follows:

public int countClumps(int[] nums) {
  int count = 0;
  if(nums.length == 0) return count;
  
  int currentNum = nums[0];
  boolean counted = false;
  
  for(int i = 1; i < nums.length; ++i){
    if(nums[i] == currentNum && !counted){ count++; counted = true; }
    else{ currentNum = nums[i]; counted = false; }
  }
  return count;
}

This solution works for every case except where the elements of nums are ubiquitous (i.e. {1,1,1,1,1,1}) In which case it returns 2. I have searched through my code time and time again and I cannot find the cause. Please help!

EDIT: Please tell me the issue with my code rather than giving me a new solution.

[xismn]

I've rewritten your code in C++, and it correctly prints 3 without having introduced any changes.

#include <iostream>

int countClumps(int array[6]) {
	int count = 0;

	int current = array[0];
	bool counted = false;

	for (int i = 1; i < 6; ++i) {
		if (current == array[i] && !counted) {
			count++;
			counted = true;
		}
		else {
			current = array[i];
			counted = false;
		}
	}
	return count;
}

int main() {

	int array[6] = {1, 1, 1, 1, 1, 1};

	std::cout << countClumps(array) << std::endl;

	return 0;
}

EDIT* read the instructions incorrectly.

[TinyTertle]

It should print 1, not 3.

[booradley60]

Once you're in a clump, you need to keep advancing the index until you've consumed everything that is the same as the current number.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

#include <iostream> int countClumps(int* arr, int arrSize) { if (arrSize <= 0) return 0; int clumpCount = 0; for (int idx = 0; idx < arrSize - 1; ++idx) { bool inClump = false; int currentItem = arr[idx]; while (idx + 1 < arrSize && currentItem == arr[idx + 1]) { inClump = true; currentItem == arr[idx + 1]; ++idx; } if (inClump) clumpCount++; } return clumpCount; } int main() { int arr1[6] = { 1, 2, 2, 3, 4, 4 }; std::cout << countClumps(arr1, 6) << std::endl; int arr2[6] = { 1, 1, 2, 1, 1 }; std::cout << countClumps(arr2, 5) << std::endl; int arr3[6] = { 1, 1, 1, 1, 1 }; std::cout << countClumps(arr3, 5) << std::endl; return 0; }

2 2 1

[TinyTertle]

Whether that actually works or not, I was actually hoping for an explanation for why what I have doesn't work. I apologize for being unclear in my original post.

[Moschops]

It's because you turn counted back to false when you shouldn't. Any time counted is true, you turn it back to false.

[dhayden]

Because any time counted is true, you end up in the else part (line 10) and set it back to false. The correct code in C++ is:

int countClumps(int nums[6]) {
    int count = 0;

    int current = nums[0];
    bool counted = false;

    for (int i = 1; i < 6; ++i) {
        if (current == nums[i]) {
            if (!counted) {
                count++;
                counted = true;
            }
        } else {
            current = nums[i];
            counted = false;
        }
    }
    return count;
}