[leetcode 26] Remove Duplicates from Sorted Array

1 题目

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.

2 思路

注意约束条件，常数空间。还有数组需要修改。提示使用双指针。

3 代码

    public int removeDuplicates(int[] nums) {
        if(nums.length == 0) return 0;
        
        int len = nums.length;
        int pre = 0;
        for(int i = 1; i < len; ++i)
        {
            if(nums[i]==nums[pre])
            {
                /*   these code can be removed
                i++;
                while(i<len && nums[i]==nums[pre]){
                    i++;
                }
                if(i<len){
                    pre++;
                    nums[pre] = nums[i];
                } */
            }else{
                pre++;
                nums[pre]=nums[i];
            }
        }
        return pre+1;
    }