Swift Coding Test Course, Finding the Building Order

Hello! Today we will learn about one of the problems frequently encountered in Swift coding tests, ‘Finding the Order of Building’. This problem will provide a good opportunity to lay the foundation of algorithms through the process of finding the order to construct buildings based on specific conditions.

Problem Definition

This problem involves returning a possible order of construction for given building information. The buildings must satisfy specific conditions, which are as follows:

• Each building has a unique height.
• If a taller building is constructed first, any building taller than that must be constructed afterwards.
• The order of the buildings must be sorted in descending order based on height.

For example, if there are buildings with heights [5, 3, 4, 1], the possible order of the buildings will be [5, 4, 3, 1], and building 5 will be constructed first.

Input and Output

Input

An integer array heights containing the heights of the buildings is given.

Output

Returns the order of buildings that can be constructed in the form of an array based on height order.

Problem Solving Approach

To solve this problem, the following steps are taken:

1. Sort the given array of building heights in descending order.
2. Traverse the sorted array and add values to the result array.
3. Return the result array.

Example

For example, if the input array is [5, 3, 4, 1], the result after sorting will be as follows:

Input: [5, 3, 4, 1]
Output: [5, 4, 3, 1]

Swift Code Implementation

Now, let’s implement the above approach in Swift.

func buildingOrder(heights: [Int]) -> [Int] {
        return heights.sorted(by: >)
    }

    // Example usage
    let heights = [5, 3, 4, 1]
    let orderedBuildings = buildingOrder(heights: heights)
    print(orderedBuildings) // Output: [5, 4, 3, 1]

The above code is a simple function that sorts the given heights array in descending order. It uses sorted(by: >) to sort the array and returns the sorted result.

Time Complexity Analysis

The time complexity of this algorithm is the same as that used for sorting the array, which is O(n log n). Here, n is the number of buildings. Since this problem is based on sorting, the time increases as the input size grows, but it can be considered an efficient method.

Conclusion

Today we explored the problem of finding the order to construct buildings using Swift. I hope this problem has helped to enhance your understanding of the fundamental concepts of algorithms and sorting. I encourage you to build your skills through more algorithmic challenges in the future!