26. 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.

class Solution {
    public int removeDuplicates(int[] nums) {
        int num =nums.length;


        
        int index=0;
        for(int i=1;i<nums.length;i++){
            if(nums[i]!=nums[i-1]){
                index++;
                nums[index]=nums[i];
            }else{
                num--;
            }

        }
        
        return num;
    }
}

思路：因爲是排好序的數組，用index哨兵來表示前index個不重複的元素，index到i爲重複的元素。