[Leetcode] 2460. Apply Operations to an Array (Easy)

概述

題目

https://leetcode.com/problems/apply-operations-to-an-array/
有點神奇的題目 XD，先從頭掃到尾，看是否有相鄰數字相同的組合，若有則前者 double、後者砍半，最後再左推非零數字

心得

本來誤解題目還想說是否由後往回做，後來確認只是模擬題，故操作完即可

Array

思路

先模擬後推數補零

程式

class Solution(object):
    def applyOperations(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        n = len(nums)
        for i in range(n-1):
            if nums[i+1] == nums[i]:
                nums[i] *= 2
                nums[i+1] = 0
        arr = []
        for i in range(len(nums)):
            if nums[i] != 0:
                arr.append(nums[i])
        while len(arr) < len(nums):
            arr.append(0)
        return arr

若是要 in-place 的話，以同向雙指針的方式做交換

class Solution(object):
    def applyOperations(self, nums):
        """
        :type nums: List[int]
        :rtype: List[int]
        """
        n = len(nums)
        for i in range(n-1):
            if nums[i+1] == nums[i]:
                nums[i] *= 2
                nums[i+1] = 0
        
        l = 0
        for r in range(n):
            if nums[l] == 0 and nums[r] != 0:
                nums[l], nums[r] = nums[r], nums[l]
            elif nums[l] != 0:
                l += 1
        
        return nums