26. Remove Duplicates from Sorted Array

Given a sorted array, remove the duplicates in place such that each element appear only once and return the new length.

Do not allocate extra space for another array, you must do this in place with constant memory.

For example,
Given input array nums=[1,1,2],

Your function should return length =2, with the first two elements of nums being1and2respectively. It doesn't matter what you leave beyond the new length.

Thoughts

Skip to check the 1st element by i == 0 and adding one to idx. Next compare current element with previous one in each iteration, idx incrementing by 1 and update the nums[i] with nums[idx] if two elements are different.

+-----------------+
|  1  |  1  |  2  |
+-----------------+
  i-1    i

skip to check

Solution

public class Solution {
    public int removeDuplicates(int[] nums) {
        int idx = 0;
        for (int i = 0; i < nums.length; i++) 
            if (i == 0 || nums[i] != nums[i - 1])
                nums[idx++] = nums[i];

        return idx;
    }
}