Leetcode: 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].

Solution:

using a flag j to indicate the current length.

If A[i] we are processing is not equal to the one before it,  add 1 to flag, and assign A[i] to A[j].

Code