给定国彩网排序数组，在​​CPP中就地删除重复的元素

每个元素只能出现一次或两次。

Example 1:

Given nums = [1, 1, 1, 2, 2, 3, 3, 3]
The function should return 6, because [1, 1, 2, 2, 3, 3]. As each element can appear 上 ly twice.

解决方案很简单。

我们将有2个变量，国彩网将保存新的长度，另国彩网用于迭代数组。

由于最多允许2个重复项，因此我们将第三个元素向后移2个元素。如果元素相同，则存在重复3次的元素。

If if array[iter] == array [len-2], then array [iter]== array [len-2]== array [len-1]

下面是伪代码：

while (iterator < array_len) 
{
	if (array[iterator] != array[new_len-2]) 
	{
		array[new_len++] = array[iterator];
	}
	iterator++;
}

我们将借助国彩网示例来理解该算法：

输入：[1、1、1、2、2、3]

pass = 1 
	Initial array = 1  1  1  2  2  3

	iterator = 2 
	new_len = 2 
	if (array[iterator] !=  array[new_len-2]) if (1 != 1) false
	Hence iterator++

	final array after pass 1 = 1  1  1  2  2  3

pass = 2 
	iterator = 3 
	new_len = 2 
	Initial array = 1  1  1  2  2  3
	if (array[iterator] != array[new_len-2]) if (2 != 1) true
	then array[new_len++] = array[iterator]; 
	iterator++ 

	final array after pass 2 = 1  1  2  2  2  3

pass = 3 

	iterator = 4 
	new_len = 3 
	Initial array = 1  1  2  2  2  3

	id (array[iterator] != array[new_len-2]) if (2 != 1) true
	then array[new_len++] = array[iterator];
	iterator++ 

	final array after pass 3 = 1  1  2  2  2  3

pass = 4 
	iterator = 5 
	new_len = 4 
	if (array[iterator] !=  array[new_len-2]) if (3 != 2) true
	then array[new_len++] = array[iterator];
	iterator++ 

	final array after pass 4 = 1  1  2  2  3  3

	iterator = 5. Hence the result

C ++解决方案

#include<iostream>
#include<vector>

using namespace std;


int removeDuplicates(int array[], int array_len) 
{
	// If the array len is less than or equal to 2 then no need to search for duplicate
	if (array_len <= 2) 
	{
		return array_len; 
	}

	// as we are allowed up to 2 duplicates, we start from the third element.
	// then we check the third element with the element 2 steps before it. If it is same,
	// it means it is the 3rd duplicate element.
	int new_len = 2;
	int iterator = 2;

	while (iterator < array_len) 
	{

		if (array[iterator] != array[new_len-2]) 
		{
			array[new_len++] = array[iterator];
		}

		iterator++;
	}
	return new_len;
}

int main()
{

	int arr[] = {1, 1, 1, 2, 2, 3};
	int array_len = 6;

	int result = removeDuplicates(arr, array_len);

	cout<<"The length of the array after the duplicates are removed = "<< result <<endl;

}

输出：

The length of the array after the duplicates are removed = 5

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