Java, LeetCode | 27. Remove Element

🚀 풀이 후기

반환해야 하는 수 k를 "제거한 수의 개수" 로 잘못 해석했습니다.

k = "제거하고 남은 수의 개수" 입니다.

🌒 문제 설명

Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The order of the elements may be changed. Then return the number of elements in nums which are not equal to val.

Consider the number of elements in nums which are not equal to val be k, to get accepted, you need to do the following things:

Change the array nums such that the first k elements of nums contain the elements which are not equal to val. The remaining elements of nums are not important as well as the size of nums.
Return k.
Custom Judge:

The judge will test your solution with the following code:

int[] nums = [...]; // Input array
int val = ...; // Value to remove
int[] expectedNums = [...]; // The expected answer with correct length.
                            // It is sorted with no values equaling val.

int k = removeElement(nums, val); // Calls your implementation

assert k == expectedNums.length;
sort(nums, 0, k); // Sort the first k elements of nums
for (int i = 0; i < actualLength; i++) {
    assert nums[i] == expectedNums[i];
}
If all assertions pass, then your solution will be accepted.

 

Example 1:

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

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

Constraints:

0 <= nums.length <= 100
0 <= nums[i] <= 50
0 <= val <= 100

🌓 문제 풀이

class Solution {
    public int removeElement(int[] nums, int val) {
    	// val 과 같지 않은 수의 개수
        int notEqualValCnt = 0;
        // 재저장할 nums 배열의 index
        int rearrangeIndex = 0;
        
        // nums배열을 순회하면서 숫자를 num 배열에 재저장합니다.
        for (int i = 0; i < nums.length; i++) {
        	// 만약 nums 배열의 값이 val 과 같으면 continue;
            if (nums[i] == val) {
                continue;
            }
            
            // nums 배열의 값이 val 과 같지 않으면,
            // cnt++
            notEqualValCnt++;
            
            // nums 배열 값을 재저장합니다.
            nums[rearrangeIndex] = nums[i];
            
            // 재저장할 다음 index++
            rearrangeIndex++;
        }
        return notEqualValCnt;
    }
}

 

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