LeetCode | 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 A = [1,1,2],

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

public class Solution {
    public int removeDuplicates(int[] A) {
        if (A.length == 0) return 0;
        if (A.length == 1) return 1;       //无需对数组A[]做任何改变
      
         int length = 1;                   //index表示的是[无重复的数组的长度]
         for (int i=1; i<A.length; i++){
             if (!(A[i-1] == A[i])) {      //A[i]与它前一个不重复，那么index++。而每当碰到一个重复，i++但index不变
                 A[length++] = A[i];       //发现重复的本次do nothing，但下次循环的时候把A[i+1]赋给无重复数组最后一个
             }                           
         }                              //如果数组中没有重复的话，length与i在for循环中是保持一致的。每发现一次重复，i就会比length大1
         return length;                  //然后直到找到不在重复的元素，赋给[无重复数组]的最后一个
    }
}