C Program to Find Factorial Using Tail Recursion

Tail recursion is a special type of recursion where the recursive call is the last action performed by the function, allowing compilers to optimize memory usage.

1. Problem Statement

Write a C program to calculate the factorial of a number using a tail-recursive function.

2. Algorithm

Step 1: Start.

Step 2: Read an integer input from the user.

Step 3: Call a recursive function passing the number and an accumulator (initialized to 1).

Step 4: Base case: if n <= 1, return the accumulator.

Step 5: Recursive case: return the function call with (n-1) and (accumulator * n).

Step 6: Print the result and exit.

3. C Program Using Tail Recursion

#include <stdio.h>

long long tail_factorial(int n, long long accumulator) {
    if (n <= 1)
        return accumulator;
    return tail_factorial(n - 1, n * accumulator);
}

int main() {
    int num = 5;
    printf("Factorial of %d is %lld", num, tail_factorial(num, 1));
    return 0;
}

4. Output

Factorial of 5 is 120

Notes

Tail recursion is memory efficient because the function does not need to perform additional operations after the recursive call, allowing the current stack frame to be reused.