Leetcode: remove duplicate

有点啰嗦。
这篇都是easy题，纪念刚开始刷题的日子，一直做嵌入式，根本不了解算法。
最开始刷的一题是remove duplicates，跟这个题一样的，都是用：
manage a new index to build array。
感叹一下，以前的同学早已经在AI领域大展拳脚，我还在这里从最简单的算法开始，安慰自己开始了就好吧。

283. Move Zeroes
     https://leetcode.com/problems/move-zeroes/description/

class Solution {
public:
    void moveZeroes(vector<int>& nums) {
        int index = 0;
        for(auto num : nums)
        {
            if(num != 0)
            {
                nums[index++] = num;
            }
        }
        
        for(; index < nums.size(); index++)
        {
            nums[index] = 0;
        }
    }
};

26. Remove Duplicates from Sorted Array
    https://leetcode.com/problems/remove-duplicates-from-sorted-array/description/

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int index = 0;
        for(auto num : nums)
        {
            if(index < 1 || num != nums[index-1])
            {
                nums[index] = num;
                index ++;
            }
        }
        
        return index;
    }
};

80. Remove Duplicates from Sorted Array II
    https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/description/

Given a sorted array nums, remove the duplicates in-place such that duplicates appeared at most twice and return the new length.

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        int index = 0;
        
        for(auto num : nums)
        {
            if(index < 2 || num != nums[index-2])
            {
                nums[index++] = num;
            }
        }
        
        return index;
    }
};