Remove Duplicates from Sorted Array

/*Description:Given a sorted array, remove the duplicates in place such that each element appear only onceand 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 A = [1,1,2],Your function should return length = 2, and A is now [1,2]*/

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方法一

//方法一 // LeetCode, Remove Duplicates from Sorted Array// 时间复杂度 O(n)空间复杂度(1)#include<iostream>#include<vector>using namespace std;class Solution {    public:        int removeDuplicates(vector<int>& nums) {            if (nums.empty()) return 0;            int index = 0;            for (int i = 1; i < nums.size(); i++) {                if (nums[index] != nums[i])                nums[++index] = nums[i];            }            return index + 1;        }};int main(){    Solution a;    vector<int> nums;    nums.push_back(1);     nums.push_back(1);     nums.push_back(2);     int b=a.removeDuplicates(nums);    cout<<b;    return 0;}

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方法二

//方法二 // LeetCode, Remove Duplicates from Sorted Array// 使用STL, 时间复杂度O(n) 空间复杂度O(1)#include<iostream>#include<vector>#include <algorithm>using namespace std;class Solution {    public:        int removeDuplicates(vector<int>& nums) {            return distance(nums.begin(), unique(nums.begin(), nums.end()));            //unique是c++模板的一个函数，在algorithm头文件中            //在STL中unique函数是一个去重函数， unique的功能是去除相邻的重复元素(只保留一个),            //其实它并不真正把重复的元素删除，是把重复的元素移到后面去了，然后依然保存到了原数组中，            //然后返回去重后最后一个元素的地址，            //因为unique去除的是相邻的重复元素，所以一般用之前都会要排一下序。        }};int main(){    Solution a;    vector<int> nums;    nums.push_back(1);     nums.push_back(1);     nums.push_back(2);     int b=a.removeDuplicates(nums);    cout<<b;    return 0;}

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方法三

//方法三 // LeetCode, Remove Duplicates from Sorted Array// 使用STL, 时间复杂度O(n) 空间复杂度O(1)#include<iostream>#include<vector>#include <algorithm>using namespace std;class Solution {public:    int removeDuplicates(vector<int>& nums) {        return distance(nums.begin(), removeDuplicates(nums.begin(), nums.end(), nums.begin()));    }    template<typename InIt, typename OutIt>    OutIt removeDuplicates(InIt first, InIt last, OutIt output) {        while (first != last) {            *output++ = *first;            first = upper_bound(first, last, *first);        }        return output;    }};int main(){    Solution a;    vector<int> nums;    nums.push_back(1);     nums.push_back(1);     nums.push_back(2);     int b=a.removeDuplicates(nums);    cout<<b;    return 0;}