Case study: Mock interview letter tiles possibilities

Dec. 1, 2019

Introduction

It is the first time I like to ask new algorithms in my mock interviews. I like to review a few algorithms before I work on an online code screen this weekend. I asked the algorithm I just reviewed called Letter tiles possibilities. Here is my post.

Mock interview case study

The transcript starts here:

	import java.io.*;
	import java.util.*;
	/*
	* To execute Java, please define "static void main" on a class
	* named Solution.
	*
	* If you need more classes, simply define them inline.
	*/
	class Solution {
	public static void main(String[] args) {
	ArrayList<String> strings = new ArrayList<String>();
	strings.add("Hello, World!");
	strings.add("Welcome to CoderPad.");
	strings.add("This pad is running Java " + Runtime.version().feature());
	for (String string : strings) {
	System.out.println(string);
	}
	possibleSequence("AAB");
	//possibleSequence("AAABBC");
	}
	public static int possibleSequence(String inp) {
	Set<String> set = generateSequences(inp.toCharArray());
	//System.out.println(set);
	System.out.println(set.size());
	return 0;
	}
	public static Set<String> generateSequences(char[] chars) {
	Set<String> set = new HashSet<>();
	if (chars.length == 1) {
	set.add(String.valueOf(chars[0]));
	return set;
	}
	for (int i = 0; i < chars.length; i++) {
	char temp = chars[0]; // put ith to 0th
	chars[0] = chars[i];
	chars[i] = temp;
	char[] rem = new char[chars.length - 1]; // take one off
	System.arraycopy(chars, 1, rem, 0, rem.length); // rem -
	Set<String> result = generateSequences(rem); // hashset
	for (String res: result) { //
	set.add(String.format("%s%s", String.valueOf(chars[0]), res)); //?
	set.add(String.format("%s", res)); // ?
	}
	/*
	"A" ?
	"B" ?
	"A"
	"B"
	Char[0] + "A"
	Char[0] + "B"
	*/
	temp = chars[0];
	chars[0] = chars[i];
	chars[i] = temp;
	}
	return set;
	}
	}
	/*
	You have a set of tiles, where each tile has one letter tiles[i] printed on it. Return the number of possible non-empty sequences of letters you can make.
	Example 1:
	Input: "AAB"
	Output: 8
	Explanation: The possible sequences are "A", "B", "AA", "AB", "BA", "AAB", "ABA", "BAA".
	Example 2:
	Input: "AAABBC"
	Output: 188
	Find permutations for all possible lengths, factor in repeating
	n! / (n - r)!
	Note:
	1 <= tiles.length <= 7
	tiles consists of uppercase English letters.
	*/

view raw LetterTilePossibilities.java hosted with ❤ by GitHub

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