leetcode-80-Remove-Duplicates-from-Sorted-Array-II

TOREVIEW

描述

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Given an integer array nums sorted in non-decreasing order, remove some duplicates in-place such that each unique element appears at most twice. The relative order of the elements should be kept the same.

Since it is impossible to change the length of the array in some languages, you must instead have the result be placed in the first part of the array nums. More formally, if there are k elements after removing the duplicates, then the first k elements of nums should hold the final result. It does not matter what you leave beyond the first k elements.

Return k after placing the final result in the first k slots of nums.

Do not allocate extra space for another array. You must do this by modifying the input array in-place with O(1) extra memory.

Custom Judge:

The judge will test your solution with the following code:

int[] nums = [...]; // Input array
int[] expectedNums = [...]; // The expected answer with correct length

int k = removeDuplicates(nums); // Calls your implementation

assert k == expectedNums.length;
for (int i = 0; i < k; i++) {
    assert nums[i] == expectedNums[i];
}

If all assertions pass, then your solution will be accepted.

Example 1:

Input: nums = [1,1,1,2,2,3]
Output: 5, nums = [1,1,2,2,3,_]
Explanation: Your function should return k = 5, with the first five elements of nums being 1, 1, 2, 2 and 3 respectively.
It does not matter what you leave beyond the returned k (hence they are underscores).

Example 2:

Input: nums = [0,0,1,1,1,1,2,3,3]
Output: 7, nums = [0,0,1,1,2,3,3,_,_]
Explanation: Your function should return k = 7, with the first seven elements of nums being 0, 0, 1, 1, 2, 3 and 3 respectively.
It does not matter what you leave beyond the returned k (hence they are underscores).

Constraints:

• 1 <= nums.length <= 3 * 104
• -104 <= nums[i] <= 104
• nums is sorted in non-decreasing order.

分析

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分别考虑两种情况，如果当前索引小于k, 直接赋值，对于后续的元素，当前写入与前面第k个元素进行比较，如果不同则保留。

解决方案1(Python)

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class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        def solveK(k):
            result = 0
            for item in nums:
                if result < k or nums[result-k] != item:
                    nums[result] = item
                    result += 1
            return result
        return solveK(2)

解决方案2（Golang）

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func removeDuplicates(nums []int) int {
    var solveK func(k int) int
    
    solveK = func(k int) int {
        result := 0
        for _, item := range nums {
            if result < k || nums[result-k] != item {
                nums[result] = item
                result++
            }
        }
        return result
    }
    return solveK(2)
}

相关问题

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• (M) Remove Duplicates from Sorted Array

题目来源