Detailed explanation of C++ function recursion: the form and implementation of recursive calls

Recursion is a programming technique in which a function calls itself. There are two common forms in C: direct recursion and indirect recursion. To implement recursion, the function must satisfy baseline conditions and recursive calls. In the actual case, recursion is used to calculate factorial. The baseline condition is that when n is 0, it returns 1. The recursive call is to multiply the function by n and call itself, decrementing n.

Detailed explanation of C function recursion

Understanding recursion

Recursion is a function Call on your own programming techniques. It allows a function to call itself one or more times within it, creating a looping structure until a specific condition is reached.

Forms of recursive calls

There are two common forms of recursive calls in C:

• Direct recursion: The function calls itself directly.
• Indirect recursion: A function calls another function, which in turn calls the original function.

Implementing recursion

To implement recursion, the function must meet the following conditions:

• Baseline conditions: Define conditions to stop the recursive process.
• Recursive call: The function calls itself, passing the appropriate parameters.

Practical case: Factorial calculation

Factorial (n!) is the product of all positive integers less than or equal to n. We can use recursion to calculate the factorial:

#include <iostream>

int factorial(int n) {
    // 基线条件
    if (n == 0) {
        return 1;
    }
    // 递归调用
    else {
        return n * factorial(n - 1);
    }
}

int main() {
    int number;
    std::cout << "请输入一个整数（>= 0）：";
    std::cin >> number;
    std::cout << number << "! = " << factorial(number) << std::endl;
    return 0;
}

Sample output:

请输入一个整数（>= 0）：5
5! = 120

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