Mastering 'Remove Element': The Ultimate Two-Pointer Quiz Quiz

1. Algorithm Understanding

   When solving the Remove Element problem, which approach ensures in-place modification of the array without allocating extra space, and why is this optimal?

   1. A. Using a two-pointer technique to overwrite unwanted values with valid ones as you iterate
   2. B. Creating a new array to store elements not equal to the target value, then copying back
   3. C. Sorting the array first and then removing all occurrences of the target value
   4. D. Reversing the array and removing the element from the new array
   5. E. Using a stack to collect valid values and then rebuilding the array

2. Code Comprehension

   Given the code: int k = 0; for (int i = 0; i u003C nums.length; i++) { if (nums[i] != val) { nums[k] = nums[i]; k++; } } What will be the value of k and the contents of nums after execution when nums = [4,4,3,2] and val = 4?

   1. A. k = 2, nums = [3,2,3,2]
   2. B. k = 2, nums = [3,2,_,_]
   3. C. k = 2, nums = [2,3,_,_]
   4. D. k = 1, nums = [3,_,_,_]
   5. E. k = 3, nums = [3,2,4,4]

3. Complexity Analysis

   Why does the Remove Element solution's time complexity remain O(n), and under which scenario could its space complexity become O(n) instead of O(1)?

   1. A. Time is O(n) due to a single full pass; space would be O(n) if a new array was used for the results
   2. B. Time becomes O(n^2) if elements are inserted at the beginning; space is always O(1) regardless
   3. C. Time is O(1) as only one pointer is moved; space becomes O(n^2) with recursion
   4. D. Time is O(log n) if the array is sorted; space remains O(1) unless extra pointers are used
   5. E. Time is O(n log n) due to inner sorting; space could be O(2n) if two arrays are used simultaneously

4. In-Place Property

   In the context of the Remove Element algorithm, what does 'in-place' modification most precisely mean if nums = [7,5,7,3] and val = 7?

   1. A. Modifying the original nums array so that the first k elements are not equal to 7, with the rest ignored
   2. B. Returning a new array excluding all 7s and leaving the original unchanged
   3. C. Changing every element to zero before returning the length
   4. D. Deleting elements from the nums array using a dynamic list structure
   5. E. Reallocating memory for each new valid element in nums

5. Pointer Mechanics

   While using two pointers (fast and slow), what unexpected issue could arise if the increment of the slow pointer is placed incorrectly, e.g., outside of the conditional block in the loop?

   1. A. Some valid elements may be overwritten or skipped, resulting in incorrect output
   2. B. All elements will be duplicated in the array, causing O(n^2) complexity
   3. C. The removal operation will only work when the target value is at the start
   4. D. An out-of-memory exception will be thrown due to infinite pointer increments
   5. E. The algorithm will reverse the order of the elements automatically