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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6.  
  7. class Ideone
  8. {
  9.  
  10. public static class User
  11. {
  12.   public static final int MINIT = 20;
  13.   public static final int MAXIT = 50;
  14.   private int iterations;
  15.  
  16.   //private static Random random = new Random();
  17.  
  18.   public void setIterations()
  19.   {
  20.     Random random = new Random();
  21.     setIterations(MINIT+random.nextInt(MAXIT-MINIT));
  22.   }
  23.  
  24.   private void setIterations(int iterations) {
  25.     this.iterations = iterations;
  26.   }
  27.   public int getIterations() {
  28.   	return iterations;
  29.   }
  30. }
  31.  
  32.   private static User user = new User();
  33.  
  34.   public static void testRandomNumbers(int SIZE) {
  35.   	final int TIMES = 30;
  36.     int results = 0;
  37.     for(int i = 0; i < TIMES; i++)
  38.     {
  39.       if (randomNumbersRun(SIZE))
  40.       {
  41.         results++;
  42.       }
  43.     }
  44.     System.out.println(results);
  45.     //System.out.println(results >= TIMES * 80 / 100);
  46.   }
  47.  
  48.   private static boolean randomNumbersRun(int SIZE)
  49.   {
  50.     ArrayList<Integer> list = new ArrayList<Integer>();
  51.     int r = User.MAXIT - User.MINIT;
  52.     //final int SIZE = 11;
  53.     for (int i = 0; i < r*SIZE; i++) {
  54.       user.setIterations();
  55.       list.add(user.getIterations());
  56.     }
  57.     return isRandom(list, r);
  58.   }
  59.  
  60.     public static boolean isRandom(ArrayList<? extends Number> randomNums, int r) {
  61.     //According to Sedgewick: "This is valid if N is greater than about 10r"
  62.     if (randomNums.size() <= 10 * r) {
  63.       return false;
  64.     }
  65.  
  66.     //PART A: Get frequency of randoms
  67.     Map<Number, Integer> ht = getFrequencies(randomNums);
  68.  
  69.     //PART B: Calculate chi-square - this approach is in Sedgewick
  70.     double n_r = (double) randomNums.size() / r;
  71.     double chiSquare = 0;
  72.  
  73.     for (int v : ht.values()) {
  74.       double f = v - n_r;
  75.       chiSquare += f * f;
  76.     }
  77.     chiSquare /= n_r;
  78.  
  79.     //PART C: According to Swdgewick: "The statistic should be within 2(r)^1/2 of r
  80.     //This is valid if N is greater than about 10r"
  81.     return Math.abs(chiSquare - r) <= 2 * Math.sqrt(r);
  82.   }
  83.  
  84.   /**
  85.    * @param nums an array of integers
  86.    * @return a Map, key being the number and value its frequency
  87.    */
  88.   private static Map<Number, Integer> getFrequencies(ArrayList<? extends Number> nums) {
  89.     Map<Number, Integer> freqs = new HashMap<Number, Integer>();
  90.  
  91.     for (Number x : nums) {
  92.       if (freqs.containsKey(x)) {
  93.         freqs.put(x, freqs.get(x) + 1);
  94.       } else {
  95.         freqs.put(x, 1);
  96.       }
  97.     }
  98.  
  99.     return freqs;
  100.   }
  101.  
  102. 	public static void main (String[] args) throws java.lang.Exception
  103. 	{
  104. 		System.out.print("  30: ");
  105. 		testRandomNumbers(30);
  106. 		System.out.print(" 100: ");
  107. 		testRandomNumbers(100);
  108. 		System.out.print(" 200: ");
  109. 		testRandomNumbers(200);
  110. 		System.out.print("1000: ");
  111. 		testRandomNumbers(1000);
  112. 	}
  113. }
Success #stdin #stdout 0.7s 380160KB
comments (?)
stdin 
Standard input is empty
stdout 
  30: 26
 100: 25
 200: 27
1000: 29
https://ideone.com/afo86g
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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