Leetcode 27- Remove Element

Leetcode 27- Remove Element from Array

by

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];
}
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

Problem Link : Remove Element – LeetCode

Solution:

Approach:
  • Use Two pointers method.
  • After shifting the val to the right side of the array.
  • Just return the value of k which is length of array excluding val.
Java Code:
  public int removeElement(int[] nums, int val) {
         int i = 0,j=0;
	    while(j < nums.length) {
	    	if (nums[j] != val) {
	            nums[i] = nums[j];
	            i++;
	        }
	    	j++;
	    
	    }
	    return i;
    }
Complexity:
  • Time complexity:O(n)
  • Space complexity:O(1)

Related posts:

Problem Solving Patterns One Must Know
Leetcode 88- Merge Sorted Array | Two Pointer
Leetcode 283 - Move Zeroes | Two Pointer

Leave a comment