[Leetcode] remove duplicates from sorted Array

Given a sorted array, remove the duplicates in place such that each element appear onlyOnceAnd 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 shocould return length = 2, and a is now [1, 2].

Https://oj.leetcode.com/problems/remove-duplicates-from-sorted-array/

Idea: Double pointer. Pointer I traversal. pointer J points to the next unique position. Note the corner case.

 

public class Solution {    public int removeDuplicates(int[] A) {        if (A == null)            return 0;        if (A.length < 1)            return A.length;        int n = A.length;        int len = 1;        for (int i = 1; i < n; i++) {            if (A[i] != A[i - 1])                A[len++] = A[i];        }        return len;    }    public static void main(String[] args) {        System.out.println(new Solution().removeDuplicates(new int[] { 1, 1, 1, 2 }));        System.out.println(new Solution().removeDuplicates(new int[] { 1, 1, 2, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5 }));        System.out.println(new Solution().removeDuplicates(new int[] {}));        System.out.println(new Solution().removeDuplicates(new int[] { 1 }));        System.out.println(new Solution().removeDuplicates(new int[] { 1, 1 }));    }}