26.Remove Duplicates from Sorted Array

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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：可以理解成双指针，一个指针是i，从i = 0开始整个遍历nums数组；另一个指针是index，也是从index = 0开始，每当nums[i] != nums[index]，就把这个元素赋给nums[index]。最后，返回index + 1就是新的Array的长度。

C++代码如下：

class Solution {public:    int removeDuplicates(vector<int>& nums) {    if(nums.empty()) return 0; //特别需要注意：当nums为空的情况    int index = 0;    for(int i = 0; i < nums.size(); ++i){        if(nums[i] != nums[index])            nums[++index] = nums[i];    }    return index + 1;    }};

Time: O(n).
Space: O(1).

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27.Remove Element
80.Remove Duplicates from Sorted Array II