HDU 1014 Uniform Generator 模拟

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. 

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

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.

 

 题目的意思就是给你一个创建随机数的方程，其中的step以及去模的mod，询问是否可以生成mod个数，如果可以，则是一个Good Choice，如果不行，则是Bad   Choice。

第一反应是这道题目需要能否构造hash，但是仔细一想其实不用可以直接进行mod次然后判断是否有存在过的数就可以了。

 1 #include<cstdio>
 2 #include<iostream>
 3 #include<cmath>
 4 #include<cstring>
 5 using namespace std;
 6 int use[100010];
 7 int main(){
 8     int step,modn,front;
 9     while(scanf("%d%d",&step,&modn)!=EOF)
10     {
11         int k=0;
12         bool bo=false;
13         memset(use,0,sizeof(use));
14         use[0]=true;
15         int seed1=0;
16         int seed2=0;
17         for (;k<modn-1;++k){
18             seed2=(seed1+step)%modn;
19             seed1=seed2;
20             if (use[seed2]==false)
21             use[seed2]=true;
22             else
23             bo=true;
24         }
25         if (bo==true)
26         printf("%10d%10d    Bad Choice\n\n",step, modn);
27         else
28         printf("%10d%10d    Good Choice\n\n",step, modn);
29     }
30     return 0;
31 }