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Decode the Coding Interview in C++: Real-World Examples

Spiral Matrix

Explore the spiral matrix traversal technique by learning to iterate over matrix layers in clockwise order. Understand how to manage row and column indices to collect elements efficiently, and analyze the algorithm's time and space complexity for effective coding interview preparation.

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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

C++
std::vector<int> spiralOrder(std::vector<std::vector<int>>& matrix) {
    return {};
}
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 to ...