linux中使用while语句计算阶乘

while计算阶乘还是比较简单的，假设需要计算1到3的阶乘：

jiechen=1 #申明变量

for bb in `seq 1 3` #计算1到3的阶乘

do

jiechen=`expr ${bb} \* ${jiechen}` #循环结算

done

echo "10! = ${jiechen}" #打印结果

#!/bin/bash

echo "请输入整数M、N(M>N)"

echo "M："

read M

#判断M是否非空且为整数

if [ -z $M ]

then

echo "M 必须非空"

exit 1

elif ! [[ $M =~ ^-?[0-9]*$ ]]

then

echo "M 必须为整数"

exit 1

fi

echo "N："

read N

#判断N是否非空且小于N的整数

if [ -z $N ]

then

echo "N 必须非空"

exit 1

elif ! [[ $N =~ ^-?[0-9]*$ ]]

then

echo "N 必须为整数"

exit 1

elif [ $M -le $N ]

then

echo "N必须小于M"

exit 1

fi

let "base = M-N"

result=1

#阶乘函数，引入result实现运算的线性增长

fac (){

base=$1

result=$2

if [ $base -gt 0 ]

then

let "result *= base"

let "base -= 1"

fac $base $result

fi

}

#计算阶乘

fac $base $result

echo "M-N的阶乘为$result"

exit 0

上次看错题目了

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