HDU 1014 Uniform Generator

                                    Uniform Generator

                    http://acm.hdu.edu.cn/showproblem.php?pid=1014   

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 21831    Accepted Submission(s): 8556

Problem Description

Computer simulations often require random numbers. One way to generate pseudo-random numbers is via a function of the form

seed(x+1) = [seed(x) + STEP] % MOD

where '%' is the modulus operator.

Such a function will generate pseudo-random numbers (seed) between 0 and MOD-1. One problem with functions of this form is that they will always generate the same pattern over and over. In order to minimize this effect, selecting the STEP and MOD values carefully can result in a uniform distribution of all values between (and including) 0 and MOD-1.

For example, if STEP = 3 and MOD = 5, the function will generate the series of pseudo-random numbers 0, 3, 1, 4, 2 in a repeating cycle. In this example, all of the numbers between and including 0 and MOD-1 will be generated every MOD iterations of the function. Note that by the nature of the function to generate the same seed(x+1) every time seed(x) occurs means that if a function will generate all the numbers between 0 and MOD-1, it will generate pseudo-random numbers uniformly with every MOD iterations.

If STEP = 15 and MOD = 20, the function generates the series 0, 15, 10, 5 (or any other repeating series if the initial seed is other than 0). This is a poor selection of STEP and MOD because no initial seed will generate all of the numbers from 0 and MOD-1.

Your program will determine if choices of STEP and MOD will generate a uniform distribution of pseudo-random numbers.

 

Input

Each line of input will contain a pair of integers for STEP and MOD in that order (1 <= STEP, MOD <= 100000).

 

Output

For each line of input, your program should print the STEP value right- justified in columns 1 through 10, the MOD value right-justified in columns 11 through 20 and either "Good Choice" or "Bad Choice" left-justified starting in column 25. The "Good Choice" message should be printed when the selection of STEP and MOD will generate all the numbers between and including 0 and MOD-1 when MOD numbers are generated. Otherwise, your program should print the message "Bad Choice". After each output test set, your program should print exactly one blank line.

 

Sample Input

3 5
15 20
63923 99999

 

Sample Output

         3         5    Good Choice

        15        20    Bad Choice

     63923     99999    Good Choice

 

题意：给出两个数step和mod，判断能否通过给定的函数生成0到mod-1间的任意数，并且按要求格式输出。

解题思路：通过分析模拟可以得出当输入两数step，mod最大公约数为1时就能满足题意，即转为判断两数是否为素数即可，但要输出格式，这是个大坑，最好用c输出。

复杂度分析： 时间复杂度：o(0)
空间复杂度：o(0)

#include<iostream>
#include<cstdio>
 #include<iomanip>
 using namespace std;
 int main()
 {
     int step,mod,r,a,b;
     while(cin>>step>>mod && mod)
     {
         a=step>mod?step:mod;
         b=step<mod?step:mod;
         while(b)
         {
             r=a%b;
             a=b;
             b=r;
         }
         if (a==1)  printf("%10d%10d    Good Choice\n\n", step, mod);
          else      printf("%10d%10d    Bad Choice\n\n", step, mod);
     }
     return 0;
 }