[Leetcode] Remove Duplicates from Sorted Array II

Posted 2020-10-22 言何午

Remove Duplicates from Sorted Array II 题解

题目来源：https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/description/

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Description

Follow up for "Remove Duplicates":

What if duplicates are allowed at most twice?

Example

Given sorted array nums = [1,1,1,2,2,3],

Your function should return length = 5, with the first five elements of nums being 1, 1, 2, 2 and 3. It doesn\'t matter what you leave beyond the new length.

Solution

class Solution {
public:
    int removeDuplicates(vector<int>& nums) {
        if (nums.empty())
            return 0;
        int size = nums.size();
        int id = 1;
        int dupTimes = 0;
        for (int i = 1; i < size; i++) {
            if (nums[i] != nums[i - 1]) {
                nums[id++] = nums[i];
                dupTimes = 0;
            } else {
                ++dupTimes;
                if (dupTimes < 2)
                    nums[id++] = nums[i];
            }
        }
        return id;
    }
};

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解题描述

这道题题意是第一版的进阶：对已经排序的数组进行原地去重（即不使用额外空间），但是允许重复元素最多出现2次。这里的解法跟第一版基本相同，只是多用了一个计数器dupTimes，每次有重复元素就计数，没有重复元素就归零，重复不超过2次就与不重复视为一样。