删除排序数组中的重复项 II

/*
 * @Author: sumBorn
 * @Date: 2022-02-22 15:02:39
 * @LastEditTime: 2022-02-23 15:05:24
 * @Description: https://leetcode-cn.com/leetbook/read/all-about-array/x9nivs/
 */

/**
 * @description: left,right双指针正常走，统计相同个数，index作为第三个指针进行数组修改
 * @param {*}
 * @return {*}
 */
public class Solution
{
    public int RemoveDuplicates(int[] nums)
    {
        int arrLength = nums.Length;
        if (arrLength <= 1) return arrLength;

        int index = 0;
        int left = 0;
        for (var right = 1; right < arrLength; right++)
        {
            bool isLast = right == arrLength - 1;
            if (nums[right] != nums[left] || isLast)
            {
                int offset = right - left;
                left += offset;

                if (offset == 1)
                {
                    index++;
                    nums[index] = nums[left];
                }
                else if (offset > 1)
                {
                    nums[index + 1] = nums[index];
                    index += 2;
                    nums[index] = nums[left];

                    if (isLast && nums[index] == nums[index - 1]) index--;
                }
            }
        }
        return ++index;
    }
}

/**
 * @description: 双指针，和简单删除重复项相似，增加了一个前一位判断
 * @param {*}
 * @return {*}
 */
public class Solution
{
    public int RemoveDuplicates(int[] nums)
    {
        int arrLength = nums.Length;
        if (arrLength <= 2) return arrLength;

        int left = 1;
        for (var right = 2; right < arrLength; right++)
        {
            if (nums[right] != nums[left] || nums[right] != nums[left - 1])
            {
                left++;
                nums[left] = nums[right];
            }
        }
        return ++left;
    }
}

/**
 * @description: 快慢指针，快指针与慢指针的前两位进行比较，慢指针记录需要替换的位置
 * @param {*}
 * @return {*}
 */
public class Solution
{
    public int RemoveDuplicates(int[] nums)
    {
        int arrLength = nums.Length;
        if (arrLength <= 2) return arrLength;

        int slow = 2;
        for (var fast = 2; fast < nums.Length; fast++)
        {
            if (nums[fast] != nums[slow - 2])
            {
                nums[slow] = nums[fast];
                slow++;
            }
        }
        return slow;
    }
}