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Decode the Coding Interview in Python: Real-World Examples

Spiral Matrix

Explore the technique of traversing an m by n matrix in spiral order using a layer-by-layer approach. Understand how to iterate matrix boundaries clockwise and learn the time and space complexity of this common coding interview problem. This lesson helps you master an efficient method for solving spiral matrix challenges.

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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

Python 3.5
def spiralOrder(matrix):
    pass
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).

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

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