Leet me code 4 - [LeetCode][C++] 26. Remove Duplicates from Sorted Array (Easy)

leet me code !

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https://leetcode.com/problems/remove-duplicates-from-sorted-array/

26. Remove Duplicates from Sorted Array

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.

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

Example 2:

Input: nums = [0,0,1,1,1,2,2,3,3,4]
Output: 5, nums = [0,1,2,3,4,_,_,_,_,_]
Explanation: Your function should return k = 5, with the first five elements of nums being 0, 1, 2, 3, and 4 respectively.
It does not matter what you leave beyond the returned k (hence they are underscores).

 

Constraints:

• 1 <= nums.length <= 3 * 104
• -100 <= nums[i] <= 100
• nums is sorted in non-decreasing order.

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문제 정리

새로운 배열을 할당하지 않고(in-place) nums 배열에 있는 수를 중복되지 않게 다시 정렬
Output - nums 배열 중 중복되지 않은 수들로 재구성한 배열의 크기

생각의 흐름

재정렬할 배열의 인덱스를 정할 i, nums 배열 전체를 순회해서 중복 여부 확인할 j
j는 nums의 크기만큼 순회, nums[i] 와 nums[j] 비교해서 인덱스 증가 여부 결정
(Two pointer..)

Solution 코드

class Solution { public: int removeDuplicates(vector<int>& nums) { int i = 0; int j = 1; int n = nums.size(); while (j < n) { if (nums[i] != nums[j]) { i++; nums[i] = nums[j]; } j++; } return i+1; } };