[LeetCode] Arrays 101: Remove Duplicates from Sorted Array

문제

입력받은 오름차순 정수 배열 nums에서 중복된 값을 제거하세요.

배열의 사이즈를 변경하지 못하는 언어일 경우, 배열의 첫 요소부터 결과를 저장하고 결과 값의 개수 k를 반환하세요.

다른 배열에 추가 메모리를 할당하지 말고 해결하세요.

 

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.

---

Code

1) splice를 통해 삭제

var removeDuplicates = function(nums) {
    for (let i = nums.length - 1; i > 0; i--) {
        if (nums[i] === nums[i - 1]) {
            nums.splice(i, 1)
        }
    }
};

2) 삭제하지 않고 해결

var removeDuplicates = function(nums) {
     let idx = 1;
     for (let i = 1; i < nums.length; i++) {
         if (nums[i - 1] !== nums[i]) {
             nums[idx++] = nums[i];
         }
     }
     return idx;
};