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Decode the Coding Interview in Swift: Real-World Examples

Spiral Matrix

Explore the spiral matrix traversal algorithm by learning to return matrix elements in clockwise order using a layer-by-layer method. Understand how to set coordinate boundaries and iterate through the matrix step-by-step. This lesson helps you develop problem-solving skills for coding interviews, focusing on algorithm design and complexity analysis.

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Description

Given an m * n matrix, you have to return all the matrix elements in spiral order. The spiral order signifies traversing the matrix in clockwise order.

Let’s review the spiral order below:

Coding exercise

Swift
import Swift
func spiralOrder(matrix: [[Int]]) -> [Int] {
    return []
}
Spiral matrix exercise

Solution

To solve this problem, we will use a layer by layer approach. In this approach, we iterate over the outer layers’ elements in clockwise order, followed by the inner layer’s elements.

For each layer, we will start from the top left corner and iterate over the elements in that layer. We define the top-left coordinates, say (r1, c1) and bottom-right coordinates, say (r2, c2).

As we explore the layers in clockwise order, we have to:

  1. Iterate the top row, (r1, c), where c ranges from c1 ...