How to use Python to implement the algorithm for solving factorial?

How to use Python to implement the algorithm for solving factorial?

Factorial is an important concept in mathematics. It refers to a number multiplied by itself minus one, then multiplied by itself minus one, and so on until it is multiplied to 1. Factorial is usually represented by the symbol "!". For example, the factorial of 5 is expressed as 5!, and the calculation formula is: 5! = 5 × 4 × 3 × 2 × 1 = 120.

In Python, we can use loops to implement a simple factorial algorithm. A sample code is given below:

def factorial(n):
    result = 1  # 初始值设为1
    
    for i in range(1, n+1):
        result *= i  # 依次乘上i的值
        
    return result

# 测试代码
num = int(input("请输入一个正整数："))
print(f"{num}的阶乘为：{factorial(num)}")

In this code, we define a function named factorial to calculate the factorial of a given positive integer n. There is a result variable with an initial value of 1 inside the function, which is used to save the factorial result. Then through a for loop, all numbers from 1 to n are multiplied in sequence, and the results are saved in result. Finally, the function returns result.

In the test part, we use the input function to obtain a positive integer input by the user, then call the factorial function to solve the factorial of the number, and print the result.

Run the code and enter a positive integer to get the factorial of the number. For example, input 5 and output 120.

In addition to using loops, Python also provides a recursive way to solve factorials. Here is a sample code for recursive implementation:

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

# 测试代码
num = int(input("请输入一个正整数："))
print(f"{num}的阶乘为：{factorial(num)}")

In this code, we use recursive calls inside the function to calculate the factorial. When n equals 0, the recursion terminates and returns 1; otherwise, the recursion calls itself, reduces the problem size to a factorial of n-1, and then multiplies the result with n and returns it.

Similarly, run the code and enter a positive integer to get the factorial of the number. For example, input 5 and output 120.

To sum up, we can use loop or recursion to implement the factorial algorithm. Which method to choose depends on the actual situation and personal preference. Either way, Python makes it easy.

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