👀 Views: 0 💬 Answers: 1 📅 Created: 2025-06-16

C recursion factorial overflow

I'm getting frustrated with I've looked through the documentation and I'm still confused about I'm working with an unexpected output from my recursive function for calculating the factorial of a number in C... The function seems to return incorrect results for certain values. Here’s my function: ```c #include <stdio.h> unsigned long long factorial(int n) { if (n < 0) { printf("behavior: Negative input\n"); return 0; // Considering negative input as invalid } if (n == 0) { return 1; } return n * factorial(n - 1); } int main() { int num = 20; // Testing with a larger number printf("Factorial of %d is %llu\n", num, factorial(num)); return 0; } ``` When I run this code, I get the correct output for values up to 20, but when I try 21, the output is incorrect, and I don't see any behavior messages. I suspect it might be related to how I'm handling large numbers, as the return type is `unsigned long long`, but I'm not sure if that's sufficient. I've also tried using different data types such as `long double` but faced similar issues. Additionally, I verified that the recursive calls are correctly reducing the input. Is there a better way to handle large factorial computations in C? Any suggestions on how to prevent overflow or improve this implementation would be greatly appreciated. What's the best practice here? Any help would be greatly appreciated! I'm developing on Windows 11 with C. What am I doing wrong? Cheers for any assistance!