Swift Coding Test Course, Summing Consecutive Numbers

In this course, we will take a closer look at one of the algorithm problems that frequently appears in coding tests, “Finding the Maximum Sum of a Continuous Subarray.” We will explain how to solve the problem using Swift and the process of writing an efficient algorithm step by step.

Problem Description

The problem is to find the maximum sum of contiguous elements from a given integer array. For example, if the array is [1, -2, 3, 4, -1, 2, 1, -5, 4], the maximum sum of contiguous elements is 3 + 4 + -1 + 2 + 1 = 9.

Input

  • Integer n (1 ≤ n ≤ 106): The number of elements in the array
  • Elements of array A (−109 ≤ Ai ≤ 109): Each element of the array

Output

  • Print the maximum sum of contiguous elements.

Problem Approach

To solve this problem, we will use the Kadane’s Algorithm as a prerequisite knowledge. This algorithm is an efficient method that can solve the problem with a time complexity of O(n).

Explanation of Kadane’s Algorithm

The Kadane’s algorithm works as follows:

  1. Traverse the array A and keep adding each element.
  2. If the current sum is less than 0, reset the sum to 0.
  3. At each step, maintain the maximum value of the current sum.

Swift Code Implementation

Now let’s implement Kadane’s algorithm in Swift.

import Foundation

func maxSubArraySum(_ nums: [Int]) -> Int {
    var maxSum = nums[0] // Initialize maximum sum of contiguous array
    var currentSum = nums[0] // Initialize current sum of contiguous array

    for i in 1..

Code Explanation

The code above consists of the following steps:

  1. It takes an integer array nums as input.
  2. Initializes the maximum sum and current sum to the first element of the array.
  3. As it traverses the array, it adds each element while calculating the maximum sum.
  4. Ultimately, it returns the maximum sum of contiguous elements.

Complexity Analysis

  • Time Complexity: O(n) - It traverses the array only once.
  • Space Complexity: O(1) - It does not use additional space except for essential variables.

Conclusion

In this course, we learned how to solve the "Finding the Maximum Sum of a Continuous Subarray" problem using Swift and about Kadane's algorithm. This algorithm can be effectively used in various coding test problems, so it's recommended to have a solid understanding of it. Furthermore, by encountering various array problems, enhance your algorithm skills!