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Decode the Coding Interview in Java: Real-World Examples

Spiral Matrix

Explore how to traverse a matrix in spiral order using a layer-by-layer approach. Understand the iteration of matrix layers clockwise and analyze the time and space complexities. This lesson helps you solve common coding interview problems involving matrix traversal efficiently in Java.

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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

Java
class Solution{
  public static List<Integer> spiralOrder(int[][] matrix) {
        return new ArrayList<Integer>();
    }
}
Spiral Matrix

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). ...