Introduction

In this blog post, we will explore how to solve the LeetCode problem "16" 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 array nums of length n and an integer target, find three integers in nums such that the sum is closest to target. Return the sum of the three integers. You may assume that each input would have exactly one solution. Example 1: Input: nums = [-1,2,1,-4], target = 1 Output: 2 Explanation: The sum that is closest to the target is 2. (-1 + 2 + 1 = 2). Example 2: Input: nums = [0,0,0], target = 1 Output: 0 Explanation: The sum that is closest to the target is 0. (0 + 0 + 0 = 0). Constraints: 3 <= nums.length <= 500 -1000 <= nums[i] <= 1000 -104 <= target <= 104

Explanation

Here's the breakdown of the solution:

• Sorting: Sort the input array nums. This enables the use of a two-pointer approach.
• Two-Pointer Approach: Iterate through the array. For each element, use two pointers to find the other two elements that, when summed with the current element, result in a sum closest to the target.

• Minimize Difference: Keep track of the sum that has the minimum absolute difference with the target.

• Runtime Complexity: O(n^2), Storage Complexity: O(1) (excluding the space for sorting, which depends on the sorting algorithm used; it could be O(log n) or O(n) in practice).

Code

    def threeSumClosest(nums, target):
    nums.sort()
    n = len(nums)
    closest_sum = float('inf')

    for i in range(n - 2):
        left = i + 1
        right = n - 1

        while left < right:
            current_sum = nums[i] + nums[left] + nums[right]

            if current_sum == target:
                return target

            if abs(current_sum - target) < abs(closest_sum - target):
                closest_sum = current_sum

            if current_sum < target:
                left += 1
            else:
                right -= 1

    return closest_sum