Introduction

In this blog post, we will explore how to solve the LeetCode problem "1207" 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

Given an array of integers arr, return true if the number of occurrences of each value in the array is unique or false otherwise. Example 1: Input: arr = [1,2,2,1,1,3] Output: true Explanation: The value 1 has 3 occurrences, 2 has 2 and 3 has 1. No two values have the same number of occurrences. Example 2: Input: arr = [1,2] Output: false Example 3: Input: arr = [-3,0,1,-3,1,1,1,-3,10,0] Output: true Constraints: 1 <= arr.length <= 1000 -1000 <= arr[i] <= 1000

Explanation

Here's the solution:

• Count Occurrences: Use a dictionary (hash map) to efficiently count the frequency of each number in the input array.
• Check Uniqueness of Counts: Use a set to store the counts. If we encounter a count that's already in the set, it means the counts are not unique, and we return False. Otherwise, we add the count to the set and continue.

• Return Result: If we successfully iterate through all the counts without finding duplicates, we return True.

• Runtime Complexity: O(n), Storage Complexity: O(n)

Code

    def uniqueOccurrences(arr: list[int]) -> bool:
    """
    Given an array of integers arr, return true if the number of occurrences of each value in the array is unique or false otherwise.
    """
    counts = {}
    for num in arr:
        counts[num] = counts.get(num, 0) + 1

    occurrences = set()
    for count in counts.values():
        if count in occurrences:
            return False
        occurrences.add(count)

    return True