Remove Element

Reader Writer - Two Pointers Approach

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# @param {Integer[]} nums
# @param {Integer} val
# @return {Integer}
def remove_element(nums, val)
    i = 0

    for j in (0..nums.length - 1)
        if nums[j] != val
            nums[i] = nums[j]
            i += 1
        end
    end

    return i
end

Identifying Problem Isomorphism

“Remove Element” (#27) can be approximately mapped to “Remove Duplicates from Sorted Array” #26.

Reasoning:

Both problems require manipulating a given array in-place.

“Remove Element” asks you to remove all instances of a specific value from the array and return the new length.
“Remove Duplicates from Sorted Array” requires you to remove all duplicates in a sorted array and return the new length.

In both problems, a similar approach can be used: You iterate through the array, keeping track of the position where the next valid number should be placed.

Both problems are about equally simple as they use similar techniques and do not involve any complex data structures. Both problems focus on in-place operations and array manipulation.

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class Solution:
    def removeElement(self, nums: List[int], val: int) -> int:
        while val in nums:
            nums.remove(val)

Problem Classification

Array Manipulation: You are working with a list (or array) and performing operations on it.
Element Removal: The problem requires removing specific elements from an array.
Data Filtering: In a broader sense, you are filtering out certain values (the given value ‘val’) from your dataset (the ’nums’ list).
In-Place Operation: You’re required to do the operation in-place, i.e., modify the existing list rather than creating a new one.

Language Agnostic Coding Drills

Understanding Lists: Understanding the basics of lists, including how to create, add elements to, remove elements from, and iterate over lists.
Searching in a List: Knowing how to find a specific element in a list. In Python, the in keyword is often used to check if a list contains a certain value.
While Loops: Understanding the basics of loops, particularly while loops, which continue executing as long as a certain condition is true.
List Modification: Familiarity with how to modify a list in place. Specifically, knowing how to remove an element from a list using the remove function. It’s crucial to understand how this impacts the list and the ongoing iteration.

Approach for solving this problem:

Initially, the solution creates a while loop, which will continue as long as the value val exists within the list nums.
Inside the loop, the remove method is used on the list nums to remove the first occurrence of the value val.
This process will continue until there are no more instances of val in nums, at which point the while loop will terminate.
The solution is designed to modify the list in place, removing any instances of val without needing to create a new list.

By understanding these key concepts, and the manner in which they combine to solve this problem, you can develop a better understanding of list manipulation and in-place algorithms.

Targeted Drills in Python

Drill 1: Understanding Lists

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# Define a list
nums = [2, 3, 3, 2]

# Add elements to the list
nums.append(1)

# Remove an element from the list
nums.remove(3)

# Print the list
print(nums)

Drill 2: Searching in a List

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# Define a list
nums = [2, 3, 3, 2]

# Check if a certain value is in the list
if 3 in nums:
    print("Found the value in the list!")
else:
    print("Value not found in the list.")

Drill 3: Understanding While Loops

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# Initialize a variable
i = 0

# Use a while loop to print a variable as long as it's less than 5
while i < 5:
    print(i)
    i += 1

Drill 4: List Modification (Removing an Element)

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# Define a list
nums = [2, 3, 3, 2]

# Remove an element from the list
nums.remove(2)

# Print the list
print(nums)

Integrated Drill: Combine all the concepts

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# Define a list
nums = [3, 2, 2, 3]
val = 3

# Use a while loop to remove all instances of `val` from the list
while val in nums:
    nums.remove(val)

# Print the final list
print(nums)