大整数阶乘新思路算法介绍及源码

#include<stdio.h> #include<stdlib.h> /*定义数组的最大位数*/ #define MAXARRAY 1000 int main() { int fac[MAXARRAY],add[MAXARRAY]; int top,n,i,j; char ch; clrscr(); while(1) { /*输入要计算的整数*/ while(1) { printf("Please input the integer to compute:\n"); scanf("%d",&n); if(n<0) { printf("Please input an integer greater -1\n"); continue; } else break; } /*初始化结果数组和进位数组*/ fac[0]=1; add[0]=0; for(j=1;j<=MAXARRAY-1;j++) { fac[j]=0; add[j]=0; } top=0; for(i=1;i<=n;i++) { /*计算进位数组add*/ for(j=0;j<=top;j++) { fac[j]=fac[j]*i; if(j==0) add[j]=fac[j]/10; else add[j]=(fac[j]+add[j-1])/10; } /*更新top的值*/ if(add[top]>=1) top++; /*计算结果数组fac*/ for(j=0;j<=top;j++) { if(j==0) fac[j]=fac[j]%10; else fac[j]=(fac[j]+add[j-1])%10; } } /*输出结果数组fac*/ printf("\n%d!=",n); for(j=top;j>=0;j--) { printf("%d",fac[j]); } printf("\n\n"); printf("Please input 'c' to continue.\n"); ch=getch(); if(ch!='c') break; } return 0; }