Search for duplicate elements in the array

[Ruhe]

Hello.
I have a pretty good working Java method, which sorts array of
strings, then searches for duplicate elements. If element is
duplicated output shows ">> hello *20 times" for example.

private void printArray()

{

String arr[] = str.split("\\n+");



Arrays.sort(arr);



for (int j = 0; j < arr.length; j++)

{

int count = 1;

for (int i = j + 1; i < arr.length; i++)

{

if (arr.compareTo(arr[j]) == 0)

{

count++;

j++;

}

}

if (count > 1)

{

System.out.println(">> " + arr[j] + " *" + count + " times");

} else

{

System.out.println(">> " + arr[j]);

}

}

}


But the problem is that I can't write this method in Ruby! How to make
this in Ruby?

 

[Robert Klemme]

Hello.
I have a pretty good working Java method, which sorts array of
strings, then searches for duplicate elements. If element is
duplicated output shows ">> hello *20 times" for example.

private void printArray()

{

String arr[] = str.split("\\n+");



Arrays.sort(arr);



for (int j = 0; j < arr.length; j++)

{

int count = 1;

for (int i = j + 1; i < arr.length; i++)

{

if (arr.compareTo(arr[j]) == 0)

{

count++;

j++;

}

}

if (count > 1)

{

System.out.println(">> " + arr[j] + " *" + count + " times");

} else

{

System.out.println(">> " + arr[j]);

}

}

}


But the problem is that I can't write this method in Ruby! How to make
this in Ruby?

This is way inefficient. You rather want a counter per element stored
in a Map (HashMap or TreeMap in Java).

dups = Hash.new 0
arr.each {|x| dups[x]+=1}
puts dups.select {|k,v| v>1}

You can have it on one line if you prefer:

puts arr.inject(Hash.new(0)) {|d,x| d[x]+=1; d}.select {|k,v| v>1}

Kind regards

robert

 

[Ruhe]

This is way inefficient. You rather want a counter per element stored
in a Map (HashMap or TreeMap in Java).

dups = Hash.new 0
arr.each {|x| dups[x]+=1}
puts dups.select {|k,v| v>1}

You can have it on one line if you prefer:

puts arr.inject(Hash.new(0)) {|d,x| d[x]+=1; d}.select {|k,v| v>1}

Kind regards

robert

Thanks a lot! This is a new level of programing knowledge for me.
I'll try to make something like this with HashMap in Java.