27. Remove Element LeetCode Solution

In this guide we will provide 27. Remove Element LeetCode Solution with best time and space complexity. The solution to Remove Element problem is provided in various programming languages like C++, Java and python. This will be helpful for you if you are preparing for placements, hackathon, interviews or practice purposes. The solutions provided here are very easy to follow and with detailed explanations.

Table of Contents

27. Remove Element LeetCode Solution image

Problem Statement of Remove Element

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];
}

See also  50. Pow(x, n)LeetCode Solution

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

Complexity Analysis

  • Time Complexity: O(n)
  • Space Complexity: O(1)

27. Remove Element LeetCode Solution in C++

class Solution {
 public:
  int removeElement(vector<int>& nums, int val) {
    int i = 0;

    for (const int num : nums)
      if (num != val)
        nums[i++] = num;

    return i;
  }
};
/* code provided by PROGIEZ */

27. Remove Element LeetCode Solution in Java

class Solution {
  public int removeElement(int[] nums, int val) {
    int i = 0;

    for (final int num : nums)
      if (num != val)
        nums[i++] = num;

    return i;
  }
}
// code provided by PROGIEZ

27. Remove Element LeetCode Solution in Python

class Solution:
  def removeElement(self, nums: list[int], val: int) -> int:
    i = 0

    for num in nums:
      if num != val:
        nums[i] = num
        i += 1

    return i
#code by PROGIEZ

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