hdu 4762 Cut the Cake （大数乘法）

猜公式：

　　ans=n/m^(n-1)

#include<stdio.h>
#include<string.h>
struct BigNum
{
    int num[100];
    int len;
};
int gcd(int a,int b)
{
    if(b==0)
        return a;
    return gcd(b,a%b);
}
BigNum mul(BigNum &a,int b)
{
    BigNum c;
    int i,len;
    len=a.len;
    memset(c.num,0,sizeof(c.num));
    if(b==0)
    {
        c.len=1;
        return c;
    }
    for(i=0; i<len; i++)
    {
        c.num[i]+=(a.num[i]*b);
        if(c.num[i]>=10)
        {
            c.num[i+1]=c.num[i]/10;
            c.num[i]%=10;
        }
    }
    while(c.num[len]>0)
    {
        c.num[len+1]=c.num[len]/10;
        c.num[len++]%=10;
    }
    c.len=len;
    return c;
}
int main()
{
    int t,m,n,i,a,b,c;
    BigNum s;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d",&m,&n);
        s.num[0]=1;
        s.len=1;
        a=n;
        for(i=1; i<n; i++)
        {
            b=m;
            c=gcd(a,m);
            a/=c;
            b/=c;
            s=mul(s,b);
        }
        printf("%d/",a);
        for(i=s.len-1; i>=0; i--)
            printf("%d",s.num[i]);
        printf("
");
    }
    return 0;
}