Answer to question from http://victorhurdugaci.com/my-interview-with-microsoft/ “You are given two arrays: before: {3, 3, 5, 8, 1} and after: {5, 3, 2, 4}. Determine what numbers were removed/added from/to the ‘before’ array in order to obtain ‘after’.”

gistfile1.java

import java.util.HashMap;
import java.util.Map;
public class BeforeAfterArray {
 
  public static void main(String[] args) {
    	
	int [] before = {3, 3, 5, 8, 1};
	int [] after = {3, 3, 3, 3};
		
	HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
		
	for (int i = 0; i < before.length; i++) {
		int key = before[i];
			
		int value = map.containsKey(key) ? map.get(key) + 1 : 1;
			
		map.put(key, value);
	}
		
	for (int i = 0; i < after.length; i++) {
		int key = after[i];
		
		if (map.containsKey(key)) {
			map.put(key, map.get(key) - 1);
            if (map.get(key) < 0) {
               System.out.println("Element " + key + " is added to resulting array.");
            }
		} else {
			System.out.println("Element " + key + " is added to resulting array.");
            
                    
		}
        
        
        
	}
		
	for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
		if (entry.getValue() > 0) {
			System.out.println("Element " + entry.getKey() + " is removed from resulting array.");
		}
	}
		
	}
}