Скачать или смотреть How to Calculate Pair and Triplet Probabilities When Rolling Dice in C

Learn how to write a C program that rolls three dice and calculates the probabilities of pairs and triplets appearing, fixing common pitfalls along the way.
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Rolling Dice in C: Calculating Pair and Triplet Probabilities

Simulating the roll of three dice and calculating probabilities can be a fun programming exercise, especially in C! However, as many programmers have experienced, errors can lurk in seemingly straightforward code, leading to unexpected results. In this guide, we'll dive into a specific case where a programmer was troubleshooting their code, which was meant to simulate rolling three dice 1,000 times and to calculate the probabilities of getting pairs and triplets.

The Problem

The initial challenge was to write a C program that performs the following tasks:

Rolls three dice 1,000 times.

Counts the number of pairs (two dice showing the same value) and triplets (all three dice showing the same value).

Calculates and prints the probabilities of rolling pairs and triplets.

However, the code that was originally written was not behaving as expected. The counters for pairs and triplets yielded incorrect results, resulting in unrealistically high numbers. Here's a simplified version of the original code snippet:

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Identifying the Issues

There were two main issues at play in the initial implementation:

1. Uninitialized Variables

The counters for pairs (coppia) and triplets (tris) need to be initialized before they are used in calculations. If they're not initialized, their default values are indeterminate, which can lead to undefined behavior in your program. This can cause your program to produce incorrect results:

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By initializing coppia and tris to zero, we ensure that our counts start from a known value.

2. Logic Flow of Conditions

The logic used to determine if a triplet occurs was not structured correctly. In the original code, if a triplet condition was true, the subsequent pair condition would also evaluate as true, thus making the triplet counter impossible to increment. To fix this issue, we need to adjust the logic in our if statements. Here's the corrected version:

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Alternatively, if you want to treat triplets as pairs (count both when a triplet is found), you can structure the code like this without an else:

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Putting It All Together

Now that we've identified the issues, let’s rewrite the complete code with the necessary corrections:

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Conclusion

By properly initializing variables and correctly structuring our conditional statements, we resolved the issues with calculating the probabilities of pairs and triplets when rolling dice in C. This lesson illustrates the importance of variable management and logical flow in programming. As you continue your coding journey, keep an eye out for these common pitfalls, and don't hesitate to reach out to the community for help when you're stuck! Happy coding!