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GeekInterview.com > Interview Questions > J2EE > Core Java
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Question: Jumble Array Values
Answer: An array A is of size N. Write a java method that jumbles all values in the array. All possible permutations must be possible and chances for each possible permutation must be equal. For example, size of array A is 3. A[0]=x, A[1]=y, A[2] =z.
Possible permutations are 3! After jumbling elements, there would be equal chances for each of xyz,yxz,... to be in the array elements.
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| October 10, 2008 09:45:18 |
#2 |
| rjlast888 |
Member Since: October 2008 Total Comments: 1 |
RE: Jumble Array Values
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import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Random;
public class TestProgram
{
/**
* @param args
*/
public static void main(String[] args)
{
int n = 20;
List a = new ArrayList(n);
List randArray = new ArrayList(n);
Map usedMap = new HashMap();
for(int idx=0; idx < n; idx++)
{
a.add(new String(Integer.toString(idx)));
}
Random generator = new Random();
for(int idx=0; idx < a.size(); idx++)
{
int position = getPosition(generator, usedMap, a.size());
randArray.add(a.get(position));
}
for(int idx=0; idx < randArray.size(); idx++)
{
System.out.println((String)randArray.get(idx));
}
}
private static int getPosition(Random generator, Map usedMap, int arraySize)
{
int pos = -1;
while(pos == -1 && !usedMap.containsKey(pos))
{
float f = generator.nextFloat() * arraySize;
int irand= (int)f;
if(irand == arraySize)
{
irand--;
}
pos = irand;
}
usedMap.put(pos, null);
return pos;
}
}
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