Remove Element

Problem Description

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number of elements in nums which are not equal to val.

Key Insights

• We need to modify the array in-place, meaning we cannot use additional space for a new array.
• The order of elements does not need to be preserved, which allows for more flexibility in our approach.
• We can use a two-pointer technique to efficiently separate values equal to val from those that are not.

Space and Time Complexity

Time Complexity: O(n)
Space Complexity: O(1)

Solution

We will use a two-pointer approach to solve this problem. The idea is to maintain a pointer for the position of the next valid element that is not equal to val. We will iterate through the array with another pointer and whenever we find an element that is not equal to val, we will place it at the position indicated by the first pointer and increment that pointer. This ensures that all valid elements are moved to the front of the array.

Code Solutions