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 nums = [1,1,2],

Your function should return length = 2, with the first two elements of nums being 1 and 2 respectively. It doesn’t matter what you leave beyond the new length.

思路：
使用双指针，使用last表示已经去重部分，i表示待判断的部分。

代码如下：

public class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums==null){
            return 0;
        }
        if(nums.length<=1){
            return nums.length;
        }
        int last=0;
        int i=1;
        while(i<nums.length){
            if(nums[last]==nums[i]){
                i++;
            }else{
                if(i-last>=2){
                    nums[last+1]=nums[i];//把下标是i的元素放到(last+1)的位置上
                    last++;
                    i++;
                }else{
                    last=i;
                    i++;
                }
            }
        }
        return last+1;
    }
}