Algorithm
Problem - Remove Element
URL - https://leetcode.com/problems/remove-element/
Level - Beginner
Details -
Given an integer array nums and an integer val, remove all occurrences of val in nums in-place. The relative order of the elements may be changed.
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 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 <= 1000 <= nums[i] <= 500 <= val <= 100
Code Examples
#1 Code Example with Javascript Programming
Code -
Javascript Programming
/**
* @param {number[]} nums
* @param {number} val
* @return {number}
*/
var removeElement = function(nums, val) {
let i = 0;
while (i < nums.length) {
if (nums[i] === val) {
nums.splice(i, 1);
} else {
++i;
}
}
};
Input
2
Output
#2 Code Example with C Programming
Code -
C Programming
int removeElement(int* nums, int numsSize, int val) {
int i, j;
i = 0;
while (i < numsSize && nums[i] != val) i ++;
for (j = i + 1; j < numsSize; j ++) {
if (nums[j] != val) {
nums[i ++] = nums[j];
}
}
return i;
}
Input
Output
#3 Code Example with C++ Programming
Code -
C++ Programming
class Solution {
public:
int removeElement(vector<int>& nums, int val) {
int i = 0, j = 0;
while(j != nums.size())
if(nums[j] == val) j++;
else nums[i++] = nums[j++];
return i;
}
};
Input
2
Output
#4 Code Example with C# Programming
Code -
C# Programming
namespace LeetCode
{
public class _027_RemoveElement
{
public int RemoveElement(int[] nums, int val)
{
var lastIndex = nums.Length - 1;
for (int i = 0; i < = lastIndex; i++)
{
if (nums[i] == val)
{
nums[i--] = nums[lastIndex--];
}
}
return lastIndex + 1;
}
}
}
Input
Output
#5 Code Example with Java Programming
Code -
Java Programming
public int removeElement(int[] nums, int val) {
int idx = 0;
for (int i = 0; i < nums.length; i++) {
if (nums[i] != val) {
nums[idx++] = nums[i];
}
}
return idx;
}
}
Input
2
Output
#6 Code Example with Python Programming
Code -
Python Programming
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
Input
2
Output
Demonstration
Leetcode - Remove Element Problem solution in Javascript