/*
阶乘最后一位非零数
*/
#include"bits/stdc++.h"
usingnamespacestd;
intexgcd(inta,intb,int&x,int&y,intc)
{
if(b==0)
{
x=c;
y=0;
returna;
}
intd=exgcd(b,a%b,x,y,c);
intt=x;
x=y;
y=t-a/b*y;
returnd;
}
intmain()
{
longlongfac[10]={1,1,2,6,24};
longlongN;
while(cin>>N)
{
intk=0;
longlongans=1;
while(N)
{
k+=N/5;
ans*=fac[N%5];
ans%=5;
N/=5;
}
k%=4;
ans*=1<<k;
ans%=5;
intx,y;
exgcd(5,2,x,y,-ans);
intres=x*5+ans;
res=(res%10+10)%10;
cout<<res<<endl;
}
}
扩展资料
阶乘亦递归方式定义：0!=1，n!=(n-1)!×n
#include<stdio.h>
intmain()
{
intn,i;
unsignedlonglongfactorial=1;
printf("输入一个整数:");
scanf("%d",&n);
//如果输入是负数，显示错误
if(n<0)
printf("Error!负数没有阶乘jiechen");
else
{
for(i=1;i<=n;++i)
{
factorial*=i;//factorial=factorial*i;
}
printf("%d!=%llu",n,factorial);
}
return0;
}
参考资料来源：百度百科—c语言
