Introduction

In this blog post, we will explore how to solve the LeetCode problem "2177" 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 integer num, return three consecutive integers (as a sorted array) that sum to num. If num cannot be expressed as the sum of three consecutive integers, return an empty array. Example 1: Input: num = 33 Output: [10,11,12] Explanation: 33 can be expressed as 10 + 11 + 12 = 33. 10, 11, 12 are 3 consecutive integers, so we return [10, 11, 12]. Example 2: Input: num = 4 Output: [] Explanation: There is no way to express 4 as the sum of 3 consecutive integers. Constraints: 0 <= num <= 1015

Explanation

Here's the breakdown of the solution:

• Mathematical Approach: The sum of three consecutive integers x, x+1, and x+2 is 3x + 3. If num is the sum, then 3x + 3 = num, so x = (num - 3) / 3. If x is an integer, we have found our three consecutive integers.

• Integer Check: We must ensure that the calculated value of x is an integer. We can check this by verifying that (num - 3) is divisible by 3.

• Array Construction: If x is an integer, we construct the array [x, x+1, x+2] and return it. Otherwise, we return an empty array.

• Complexity: O(1) runtime, O(1) storage.

Code

    def sum_of_three(num: int) -> list[int]:
    """
    Given an integer num, return three consecutive integers (as a sorted array) that sum to num.
    If num cannot be expressed as the sum of three consecutive integers, return an empty array.

    For example:
    sum_of_three(33) == [10, 11, 12]
    sum_of_three(4) == []
    """
    if (num - 3) % 3 == 0:
        x = (num - 3) // 3
        return [x, x + 1, x + 2]
    else:
        return []