Introduction

In this blog post, we will explore how to solve the LeetCode problem "1338" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like Chatmagic, we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

Problem Statement

You are given an integer array arr. You can choose a set of integers and remove all the occurrences of these integers in the array. Return the minimum size of the set so that at least half of the integers of the array are removed. Example 1: Input: arr = [3,3,3,3,5,5,5,2,2,7] Output: 2 Explanation: Choosing {3,7} will make the new array [5,5,5,2,2] which has size 5 (i.e equal to half of the size of the old array). Possible sets of size 2 are {3,5},{3,2},{5,2}. Choosing set {2,7} is not possible as it will make the new array [3,3,3,3,5,5,5] which has a size greater than half of the size of the old array. Example 2: Input: arr = [7,7,7,7,7,7] Output: 1 Explanation: The only possible set you can choose is {7}. This will make the new array empty. Constraints: 2 <= arr.length <= 105 arr.length is even. 1 <= arr[i] <= 105

Explanation

Here's the solution approach, complexity analysis, and Python code:

• Count Frequencies: Calculate the frequency of each number in the input array.
• Greedy Removal: Sort the frequencies in descending order. Greedily remove the numbers with the highest frequencies until at least half the elements are removed.

• Count the Removed Sets: return the number of integers we had to remove.

• Time Complexity: O(n log n), dominated by sorting the frequencies. Space Complexity: O(n), for storing the frequencies in a dictionary/hash map.

Code

    def minSetSize(arr: list[int]) -> int:
    """
    Given an integer array arr, return the minimum size of the set so that at
    least half of the integers of the array are removed.

    Example:
    Input: arr = [3,3,3,3,5,5,5,2,2,7]
    Output: 2
    Explanation: Choosing {3,7} will make the new array [5,5,5,2,2] which has
    size 5 (i.e equal to half of the size of the old array).
    Possible sets of size 2 are {3,5},{3,2},{5,2}.
    Choosing set {2,7} is not possible as it will make the new array
    [3,3,3,3,5,5,5] which has a size greater than half of the size of the old
    array.

    Args:
        arr (list[int]): the input array

    Returns:
        int: the minimum size of the set
    """
    counts = {}
    for num in arr:
        counts[num] = counts.get(num, 0) + 1

    frequencies = sorted(counts.values(), reverse=True)
    removed_count = 0
    removed_set_size = 0
    half_size = len(arr) // 2

    for freq in frequencies:
        removed_count += freq
        removed_set_size += 1
        if removed_count >= half_size:
            break

    return removed_set_size