[LeetCode] Remove Duplicates from Sorted Array

https://leetcode.com/explore/interview/card/top-interview-questions-easy/92/array/727/

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

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.

이미 오름차순 정렬된 리스트가 주어지며, 해당 리스트의 중복원소를 모두 제거한 후 상대적인 정렬도는 유지해야 한다.

• python1
  : 포인터를 써서 체크해나가는 방법.

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        if len(nums) < 2 :
            return
        
        initial = nums[0]
        pointer =0
        for num in nums :
            if num > initial:
                pointer += 1
                nums[pointer] = num
                initial = num
        
        return(pointer+1)

• python2 : set을 이용하면 더 간단한데, 문제의 의도와는 멀어지는 듯 하다.

class Solution:
    def removeDuplicates(self, nums: List[int]) -> int:
        nums[:] = sorted(set(nums))
        return len(nums)

• Java solution

class Solution {
    public int removeDuplicates(int[] nums) {
            if(nums.length < 2) 
                return nums.length;
            int pointer = 1;
            int num = nums[0];
        
            for(int i=0; i < nums.length; i++){
                if(nums[i] > num){
                    nums[pointer++] = nums[i];
                    num = nums[i];
                }
            }
    return pointer;
    }

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• 풀었던 것도 또 풀어보자.
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