Introduction

In this blog post, we will explore how to solve the LeetCode problem "1" 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 nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order. Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Explanation: Because nums[0] + nums[1] == 9, we return [0, 1]. Example 2: Input: nums = [3,2,4], target = 6 Output: [1,2] Example 3: Input: nums = [3,3], target = 6 Output: [0,1] Constraints: 2 <= nums.length <= 104 -109 <= nums[i] <= 109 -109 <= target <= 109 Only one valid answer exists. Follow-up: Can you come up with an algorithm that is less than O(n2) time complexity?

Explanation

Here's a solution that addresses the prompt, including the explanation, complexity analysis, and Python code:

• Key Approach:

  • Use a hash map (dictionary in Python) to store each number in the array along with its index.
  • Iterate through the array, and for each number, check if target - number exists in the hash map.
  • If it exists and the index is different from the current index, return the indices.

• Complexity:

  • Runtime Complexity: O(n) - due to the single pass through the array and O(1) average time complexity for hash map lookups and insertions.
  • Storage Complexity: O(n) - in the worst case, we might store all n elements of the input array in the hash map.

Code

    def twoSum(nums, target):
    """
    Finds two numbers in the array that add up to the target.

    Args:
        nums (list of int): An array of integers.
        target (int): The target sum.

    Returns:
        list of int: A list containing the indices of the two numbers.
    """
    num_map = {}
    for index, num in enumerate(nums):
        complement = target - num
        if complement in num_map:
            return [num_map[complement], index]
        num_map[num] = index