Leetcode 26: Remove Duplicates from Sorted Array

Problem:

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].

Analysis:
As it is a sorted array, duplicated elements are neighboring with each other.
We can easily using two pointers to copy the first met element to the end of non-duplicated list.

Code:

public class Solution {
    public int removeDuplicates(int[] A) {
        if(A==null){
            return -1;
        }else if(A.length<=1){
            return A.length;
        }
        int len=0;// the last element
        for(int i=1;i<A.length;i++){//i is another pointer
            if(A[i]!=A[len]){
                A[++len]=A[i];
            }
        }
        return len+1;
    }
}