CC-8 : Find unique and repeating elements in an array.

Description:

Given an input array of String, find the return the list of unique words and the list of repeating words.

Test cases and expected outputs:

Input Parameters	Expected outputs
strArray1 = {"listen", "near", "swim", "morning", "listen"};	Unique Elements : near,swim,morning Repeating Elements : listen
strArray = {"peace", "road", "ate", "ate", "tree", "fly", "tree"};	Unique Elements : fly,road,peace Repeating Array : ate,tree

Pseudocode:

The java method should accept following input parameters: arr (String array).

Initialize a variable uniqueWords of type HashSet to hold the unique elements of arr.

Initialize a variable repeatWords of type HashSet to hold the repeating elements of arr.

Using a for loop iterate through arr, using idx as a loop variable with initial value 0 and increment idx till it reaches arr1.length-1:

if uniqueWords does not contain arr[idx]:

Add arr[idx] to uniqueWords.

if uniqueWords does contains arr[idx]:

Add arr[idx] to repeatWords.

At completion of above loop, remove all elements of repeatWords from uniqueWords using HashSet.removeAll() method. Now, uniqueWords contains all the unique words and repeatWords contains all the repeated words.

Initialize a 2 dimensional String array retVal with 2 rows.

Use an iterator to access elements from uniqueWords and add the same to String array retVal[0]. Use another iterator to access elements from repeatWords and add the same to String array retVal[1]. Return retVal.

Code:

public String[][] setFindUniqueAndRepeating(String[] arr) {
	HashSet<String> uniqueWords=new HashSet<String>();
	HashSet<String> repeatWords=new HashSet<String>();
	for (int idx=0; idx< arr.length; idx++) {
		if ( ! uniqueWords.contains(arr[idx])) {
			uniqueWords.add(arr[idx]);
		}else {
			repeatWords.add(arr[idx]);
		}
	}
	uniqueWords.removeAll(repeatWords);
	String[][] retVal=new String[2][];
	retVal[0]=new String[uniqueWords.size()];
	retVal[1]=new String[repeatWords.size()];
	int idx=0;
	Iterator itr=uniqueWords.iterator();
	while (itr.hasNext()) {
		retVal[0][idx]=(String)itr.next();
		idx++;
	}
	idx=0;
	itr=repeatWords.iterator();
	while (itr.hasNext()) {
		retVal[1][idx]=(String)itr.next();
		idx++;
	}
	return retVal;
}

Click here to download and run code and test cases !

Below fully running code can be copied and run on Eclipse or other Java IDEs. Refer the classname in code below. If the class name below is "A", save the code below to a file named A.java before running it. Be sure to try your own test cases to enhance your understanding ! You can also tweak the code to optimize or add enhancements and custom features.

import java.util.HashSet;
import java.util.Iterator;


public class SetFindUniqueAndRepeating {
	
public String[][] setFindUniqueAndRepeating(String[] arr) {
	HashSet<String> uniqueWords=new HashSet<String>();
	HashSet<String> repeatWords=new HashSet<String>();
	for (int idx=0; idx< arr.length; idx++) {
		if ( ! uniqueWords.contains(arr[idx])) {
			uniqueWords.add(arr[idx]);
		}else {
			repeatWords.add(arr[idx]);
		}
	}
	uniqueWords.removeAll(repeatWords);
	String[][] retVal=new String[2][];
	retVal[0]=new String[uniqueWords.size()];
	retVal[1]=new String[repeatWords.size()];
	int idx=0;
	Iterator itr=uniqueWords.iterator();
	while (itr.hasNext()) {
		retVal[0][idx]=(String)itr.next();
		idx++;
	}
	idx=0;
	itr=repeatWords.iterator();
	while (itr.hasNext()) {
		retVal[1][idx]=(String)itr.next();
		idx++;
	}
	return retVal;
}

	
public static void main(String[] args) {
		
	SetFindUniqueAndRepeating sp=new SetFindUniqueAndRepeating();
	String[][] retVal;
	try {
	String[] strArray1 = {"listen", "near", "swim", "morning", "listen"};
	printArraySummary(strArray1, "Original Array");
	retVal=sp.setFindUniqueAndRepeating(strArray1);
	printArraySummary(retVal[0], "Unique Elements");
	printArraySummary(retVal[1], "Repeating Array");
			
	String[] strArray2 = {"peace", "road", "ate", "ate", "tree", "fly", "tree"};
	printArraySummary(strArray2, "Original Array");
	retVal=sp.setFindUniqueAndRepeating(strArray2);
	printArraySummary(retVal[0], "Unique Elements");
	
	printArraySummary(retVal[1], "Repeating Array");
			
	String[] strArray3 = {"join", "roar", "smile", "art", "more", "dear", "pen"};
	printArraySummary(strArray3, "Original Array");
	retVal=sp.setFindUniqueAndRepeating(strArray3);
	printArraySummary(retVal[0], "Unique Elements");
	printArraySummary(retVal[1], "Repeating Array");
			
	String[] strArray4 = {"here", "good", "here", "good"};
	printArraySummary(strArray4, "Original Array");
	retVal=sp.setFindUniqueAndRepeating(strArray4);
	printArraySummary(retVal[0], "Unique Elements");
	printArraySummary(retVal[1], "Repeating Array");
			
	}catch (Exception exception) {
	System.out.print("Exception,"+ exception);
	exception.printStackTrace();
				
	}
}
			
public static void printArraySummary(String[] intArray, String label) throws Exception {
   	// Case 1: The input Array is null !!
	if (intArray == null) { System.out.println("\n\n Input Array was null !! \n"); return; }
	// Case 2: Print input Array by index (first to last)
	System.out.println();
	System.out.println("************************************************************************");
	System.out.print(label+" : ");
	int arrayIndex=0;
	for (arrayIndex=0; arrayIndex< intArray.length; arrayIndex++) {
			System.out.print(intArray[arrayIndex]);
			if (arrayIndex< intArray.length-1) {System.out.print(",");}
	} 
	System.out.println();
	System.out.println("*************************************************************************");
	System.out.println();
	Thread.sleep(2000);
	return;
}				
		
		

}