Solution to problem 26 “Remove Duplicates from Sorted Array” from LeetCode.

Problem Statement

Given a sorted array of numbers nums. You need to remove duplicates inside this array and return the new length of the array. You cannot allocate space for a new array.

Example 1

nums = [1,1,2],

Function should return `2`. That is, the zeroth and first elements of the array should be `1` and `2` respectively.

It doesn't matter what comes after in the array

Example 2

nums = [0,0,1,1,1,2,2,3,3,4],

Function should return `5`. The first five elements of the array should be 0,1,2,3,4 and 5.

It doesn't matter what comes after in the array

Solution

Two Pointers

Algorithm idea:

There are two pointers:

• The first looks at the current element (at each step it moves to the next element)
• The second looks at the last non-repeating element

When the element at the current pointer becomes greater than the element at the second pointer:

• Move the second pointer to the next element
• Assign to the address of the second pointer the value from the current pointer

Return second pointer + 1

func removeDuplicates(nums []int) int {
    if len(nums) <=1 {
         return len(nums)
    }
    lidx :=0

    for idx:=1;idx <len(nums);idx++ {
        if nums[idx] > nums[lidx] {
             lidx ++
            nums[lidx] = nums[idx]

        }
    }

    return lidx+1
}