26. Remove Duplicates from Sorted Array Leetcode Java

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 A = [1,1,2],

Your function should return length = 2, and A is now [1,2].

Solution:

The algorithm is to maintain a non duplicates elements index, move non-duplicate elements to the index position. After one time iteration all elements from 0 to our index will be non-duplicates.

 public int removeDuplicates(int[] A) {  
    if(A==null || A.length==0) return 0;  
    int index=1;  
    for(int i=1;i<A.length;i++){  
      if(A[i]!=A[i-1]){  
        A[index]=A[i];  
        index++;  
      }  
    }  
    return index;  
   }