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  1. import java.util.Arrays;
  2. public class Main{
  3.     public static void main(String[] args){
  4.  
  5.             double[][] probabilities;
  6.             int numMines = 4;  //The number of mines you have
  7.             double firstProbability = .5;  //The probability that a mine has gold at first.  50% in example problem.  Express as a number between 0 and 1
  8.             double probabilityAfterFound = .9;  //The probability that a mine has gold once one gold has been found.  90% in example problem.  
  9.  
  10.             probabilities = new double[numMines + 1][numMines+1];
  11.             probabilities[0][0]=1;
  12.             for(int mine = 1; mine <= numMines; mine++){
  13.                 probabilities[mine][0] = probabilities[mine-1][0]*(1-firstProbability);
  14.                 probabilities[mine][1] = probabilities[mine-1][0]*(firstProbability) + probabilities[mine-1][1]*(1-probabilityAfterFound);
  15.                 for(int numGolds = 2; numGolds <= numMines; numGolds++){
  16.                     probabilities[mine][numGolds] = probabilities[mine-1][numGolds-1]*probabilityAfterFound + probabilities[mine-1][numGolds]*(1-probabilityAfterFound);
  17.                 }
  18.             }
  19.  
  20.             for(int mine = 0; mine <= numMines; mine++){
  21.                 System.out.println(Arrays.toString(probabilities[mine]));
  22.             }
  23.  
  24.             double expectedGolds = 0;
  25.             for(int numGolds = 0; numGolds<=numMines; numGolds++){
  26.                 expectedGolds+=numGolds*probabilities[numMines][numGolds];
  27.             }
  28.             System.out.println("You expect to find gold " + expectedGolds + " times.");
  29.             System.out.println("You expect to find gold at least once " + ((1-probabilities[numMines][0])*100) + "% of the time");
  30.     }
  31. }
Success #stdin #stdout 0.11s 320256KB
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Standard input is empty
stdout
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[1.0, 0.0, 0.0, 0.0, 0.0]
[0.5, 0.5, 0.0, 0.0, 0.0]
[0.25, 0.3, 0.45, 0.0, 0.0]
[0.125, 0.155, 0.315, 0.405, 0.0]
[0.0625, 0.078, 0.171, 0.324, 0.36450000000000005]
You expect to find gold 2.85 times.
You expect to find gold at least once 93.75% of the time
https://ideone.com/iyESR5
language:
Java (HotSpot 12)
created:
9 years ago
visibility:
public

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