> For the complete documentation index, see [llms.txt](https://hao-fu-1.gitbook.io/oj/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hao-fu-1.gitbook.io/oj/multiple-pointers/shuang-zhi-zhen-zhi-xian-hou-zhi-zhen/remove-duplicates-from-sorted-array.md).

# 26. Remove Duplicates from Sorted Array

https\://leetcode.com/problems/remove-duplicates-from-sorted-array/description/

> 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.

## Thoughts

对给定数组压缩：将重复元素剔除。前后双指针，后指针每次前进一格并比较当前字符和后面是否一致（或到了最后一个字符），一致时跳过，否则在前指针位置开始替换。

## Code

```python
class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        j = 0
        for i, num in enumerate(nums):
            if i == len(nums) - 1 or num != nums[i + 1]:
                nums[j] = nums[i]
                j += 1
        return j
        
```

```cpp
class Solution {
    public int removeDuplicates(int[] nums) {
        int pos, i;
        for (i = 0, pos = 0; i < nums.length; i++) {
            if (i == nums.length - 1 || nums[i] != nums[i + 1]) {
                nums[pos++] = nums[i];
            }
        }

        return pos;
    }
}
```

## Analysis

时间复杂度O(n), 空间O(1).