hdu 1014 Uniform Generator

迷南。 2022-06-12 02:19 153阅读 0赞

# Uniform Generator #

**Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)  
Total Submission(s): 29167 Accepted Submission(s): 11616**

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
      
       
      
       
    
      
       
      
       
        
       题目大意：按照公式求随机数，最后看随机数是否在0-MOD-1之间都只出现一次，若是则输出Good Choice，否则输出Bad Choice。
      
       
      
       
    
      
       
      
       
        
       题目解析：这是一个简单的模拟题，首先用公式求出随机数，在排序比较就可以得出答案。
      
       
      
       
    
      
       
      
       
        
       代码：
      
       
      
       
       
        #include<iostream>
    #include<cstdio>
    #include<algorithm>
    #include<cstring>
    using namespace std;
    
    int seed[100000+5];
    int main()
    {
        int step,mod;
        memset(seed,0,sizeof(seed));
        while(cin>>step>>mod)
        {
            int cnt=0;
            seed[0]=0;
            for(int i=1;i<mod;i++)
            {
                seed[i]=(seed[i-1]+step)%mod;
            }
            sort(seed,seed+mod);
            for(int i=0;i<mod;i++)
            {
                if(seed[i]!=i)
                    break;
                else
                    cnt++;
            }
            if(cnt==mod)
                printf("%10d%10d    Good Choice\n\n",step,mod);
            else
               printf("%10d%10d    Bad Choice\n\n",step,mod);
        }
        return 0;
    }