Скачать или смотреть How to Count Pairs of Socks in an Array Using Python

Discover how to efficiently count pairs of socks by color in an array, including a step-by-step guide and sample Python code.
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This video is based on the question https://stackoverflow.com/q/65929866/ asked by the user 'John Thomas' ( https://stackoverflow.com/u/9393218/ ) and on the answer https://stackoverflow.com/a/65929911/ provided by the user 'Lex Nasser' ( https://stackoverflow.com/u/10627995/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Count Pairs of Socks in an Array Using Python

If you’ve ever found yourself buried under a pile of socks, you know the struggle of pairing them by color. This is a classic problem that can be solved with programming – specifically, using Python to count how many pairs of socks there are based on their colors. In this guide, I'll explain how to approach this problem and present a solution that leverages Python’s built-in capabilities.

The Problem

Imagine you have a pile of socks represented in an array of integers, where each integer corresponds to the color of a sock. For instance:

[[See Video to Reveal this Text or Code Snippet]]

In this case, the goal is to determine how many pairs of socks match by color. For the sample array above, the output should be 3 pairs: two pairs of color 2 and one pair of color 1.

Understanding the Existing Approach

In trying to solve this problem, the initial code provided attempts to count pairs but only looks for consecutive matches, which is not sufficient. Here’s the provided code:

[[See Video to Reveal this Text or Code Snippet]]

Issues with the Original Approach

Only Consecutive Matches: The code checks if the current sock matches the next sock only. This limits the possibility of counting pairs effectively.

Logic Errors: The condition (pairs / 2 == 0) doesn't correctly check for pairs.

Given these shortcomings, we can adopt a different strategy.

A Better Approach Using a Dictionary

A more effective way to count pairs is to use a dictionary to map each color to its count. Here’s how you can implement this:

Step-by-Step Solution

Initialize a Dictionary: Create an empty dictionary to store counts of each color.

Count the Colors: Loop through the array and populate the dictionary with color counts.

Calculate Pairs: After counting, divide each color's count by 2 to determine how many pairs can be formed.

Sample Code

Here’s a more effective implementation:

[[See Video to Reveal this Text or Code Snippet]]

How It Works

Counting: The setdefault method initializes a new count for each sock color and increments it.

Summing Pairs: The final step calculates how many pairs can be formed for each color by using integer division (//).

Running the Code

To get the final number of pairs, simply call the function with your sock array:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Pairing socks might not seem like a coding challenge at first, but it’s a great example of how to utilize data structures in Python to solve problems efficiently. By switching from a simple iterative approach to using a dictionary for counting, we greatly improved our solution.

Feel free to try out the code and modify the sock array to see how your pairs count changes. Happy coding!