（简单）计算斐波那契数列与阶乘

斐波那契数列

python

def fibonacci(n):
    if n <= 0:
        return "Invalid input"
    elif n == 1:
        return 0
    elif n == 2:
        return 1
    else:
        prev_1 = 0
        prev_2 = 1
        for _ in range(n - 2):
            current = prev_1 + prev_2
            prev_1, prev_2 = prev_2, current
        return prev_2

shell

#!/bin/bash

fibonacci() {
    local n=$1
    if [ $n -le 0 ]; then
        echo "Invalid input"
    elif [ $n -eq 1 ]; then
        echo 0
    elif [ $n -eq 2 ]; then
        echo 1
    else
        prev_1=0
        prev_2=1
        for ((i=2; i<n; i++)); do
            current=$((prev_1 + prev_2))
            prev_1=$prev_2
            prev_2=$current
        done
        echo $prev_2
    fi
}

# 测试函数
echo $(fibonacci 5)  # 输出：3
echo $(fibonacci 8)  # 输出：13

阶乘

思路是一样的，只是算式不一样，代入几何坐标中会更好理解

python

def factorial(n):
    if n < 0:
        return "Invalid input"
    elif n == 0 or n == 1:
        return 1
    else:
        result = 1
        for i in range(2, n + 1):
            result *= i
        return result

print(factorial(5))  # 输出：120
print(factorial(8))  # 输出：40320

shell

#!/bin/bash

factorial() {
    local n=$1
    if [ $n -lt 0 ]; then
        echo "Invalid input"
    elif [ $n -eq 0 ] || [ $n -eq 1 ]; then
        echo 1
    else
        result=1
        for ((i=2; i<=n; i++)); do
            result=$((result * i))
        done
        echo $result
    fi
}

# 测试函数
echo $(factorial 5)  # 输出：120
echo $(factorial 8)  # 输出：40320