One interesting interview question -
You are given a list or array of words & you have to create sets of anagrams such that all anagram words are in one set. So you can have multiple different sets, all having anagram words.
e.g. Input : "DOG", "CAT","TAC","GOD","ACT"
       Output : ACT=[ACT, TAC, CAT],
                     DGO=[DOG, GOD]

Check a simpler version from Round1 asked in Expedia here.
Below is the code & later I have attached the code file also to download & use -

​import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Random;
import java.util.Set;
import java.util.stream.IntStream;

/**
 * @author Nitin Agrawal
 * 
 */
public class AnagramSets {

private Map<String, Set<String>> anagramsSets = new HashMap<>();
private static int count = 0;

public static void main(String[] args) {

AnagramSets anagramSets = new AnagramSets();
String[] input = {"DOG", "CAT","TAC","GOD","ACT"};
// String[] input = anagramSets.generateStringArray(500000);
// One Way
long start = System.currentTimeMillis();
anagramSets.findSets(input);
anagramSets.anagramsSets.forEach((a,b) -> {
if(b.size() > 1)
count++;
});
System.out.println("Count : " + count);
System.out.println(System.currentTimeMillis()-start);

count = 0;
anagramSets.anagramsSets.clear();

// Another Way
start = System.currentTimeMillis();
List<Block> list = new ArrayList<>();
int len = input.length;
for(int i = 0; i < len; i++) {
list.add(new Block(input[i], i));
}

Collections.sort(list);
Block cur = list.get(0);
Set<String> anagrams = null;
for(int i = 1; i < len; i++) {
if((anagrams=anagramSets.anagramsSets.get(cur.sorted)) == null) {
anagrams = new HashSet<>();
anagramSets.anagramsSets.put(cur.sorted, anagrams);
}
if(list.get(i).equals(cur)) {
anagrams.add(input[list.get(i).index]);
} else {
anagrams.add(input[cur.index]);
anagramSets.anagramsSets.put(cur.sorted, anagrams);
anagrams = new HashSet<>();
anagrams.add(input[list.get(i).index]);
anagramSets.anagramsSets.put(list.get(i).sorted, anagrams);
cur = list.get(i);
}
}
anagramSets.anagramsSets.forEach((a,b) -> {
if(b.size() > 1)
count++;
});
System.out.println("Count : " + count);
System.out.println(System.currentTimeMillis()-start);
}

private void findSets(String[] words) {
Arrays.asList(words)
.parallelStream()
.forEach(this::addToSet);
}

private void addToSet(String word) {
char[] chars = null;
Arrays.sort((chars=word.toCharArray()));
String key = new String(chars);
Set<String> set = null;
if((set=anagramsSets.get(key)) == null) {
set = new HashSet<>();
set.add(word);
anagramsSets.put(key, set);
} else {
set.add(word);
}
}

private String[] generateStringArray(int size) {
String[] array = new String[size];
IntStream.range(0, size)
.forEach(a -> {
char ch1 = (char)new Random().ints(65, 75).findFirst().getAsInt();
char ch2 = (char)new Random().ints(75, 85).findAny().getAsInt();
char ch3 = (char)new Random().ints(70, 80).findAny().getAsInt();
char ch4 = (char)new Random().ints(80, 90).findAny().getAsInt();
String str = ""+ch1+ch2+ch3+ch4;
array[a] = str;
});
return array;
}

static class Block implements Comparable<Block> {
String sorted;
int index;
public Block(String word, int index) {
this.index = index;
char[] chars = word.toCharArray();
Arrays.sort(chars);
sorted = new String(chars);
}

@Override
public boolean equals(Object obj) {
if(obj instanceof Block)
return ((Block)obj).sorted.equals(sorted);
return false;
}

@Override
public int compareTo(Block o) {
return sorted.compareTo(o.sorted);
}

@Override
public String toString() {
return sorted;
}
}
}

anagramsets.java
File Size:	3 kb
File Type:	java

Download File

---