廈門大學OJ 1044 僞僞隨機數產生器

http://acm.xmu.edu.cn/JudgeOnline/problem.php?id=1044

代碼：

#include<stdio.h>
#include<stdlib.h>

int main(void)
{   
    int x,y;
    long long a,b,a_bit,b_bit,p,temp;
    double anchor;
    
    //freopen("1044_in.txt","r",stdin);
    scanf("%d%d", &x, &y);
    if(0 == x) 
    {
        printf("0");
        exit(0);
    }
    a = 1;
    b_bit = 0;
    p = 0;
    anchor = 1;
    temp = x;
    while(temp/=10){anchor*=10,p++;};
    anchor/=x;
    while(b_bit<y)
    {    
        a_bit = b_bit;   
        b = a;
        p++; 
        anchor*=10;
        a=anchor; 
        if(anchor - (int)anchor != 0.0) a++;   
        b_bit += (a-b)*p; 
    }
    if(y == b_bit) printf("%lld\n",((a-1)%10)*(x%10)%10);   
    else 
    {   
        y-=a_bit;
        if(y%p)
        {
            a=y/p+b;
            b=p-y%p;
        }
        else
        {
            a=y/p+b-1;
            b=0;
        }
        temp=x*a;
        while(b--)
        {
            temp/=10;
        }
        printf("%d",temp%10);
    }
    return 0;   
}

思路：

1、不能太暴力，會超時。

2、long long。