poj 3406 组合数的最后非0数

#include<stdio.h>int get(int x,int n){if(n==0)return 0;elsereturn (n/x)+get(x,n/x);}int get1(int x,int n){if(n==0)return 0;elsereturn (n/10)+((n%10)>=x)+get1(x,n/5);}int get2(int x,int n){if(n==0)return 0;elsereturn get2(x,n/2)+get1(x,n);}int t[3][4]={{6,2,4,8},{1,3,9,7},{1,7,9,3}};int main(){int n,m,n2,n3,n5,n7,n9,res=1;scanf("%d%d",&n,&m);n2=get(2,n)-get(2,n-m)-get(2,m);n5=get(5,n)-get(5,n-m)-get(5,m);n3=get2(3,n)-get2(3,n-m)-get2(3,m); n7=get2(7,n)-get2(7,n-m)-get2(7,m); n9=get2(9,n)-get2(9,n-m)-get2(9,m);n3+=n9*2;if(n2<n5)printf("5\n");else{if(n2!=n5){res*=t[0][(n2-n5)%4];}res*=t[1][n3%4];res*=t[2][n7%4];printf("%d\n",res%10);}}