KodeSeeker

Studying for a Tech Interview Sucks, so Here's a Cheat Sheet to Help

This list is meant to be a both a quick guide and reference for further research into these topics. It's basically a summary of that comp sci course you never took or forgot about, so there's no way it can cover everything in depth. It also will be available as a gist on Github for everyone to edit and add to.

Data Structure Basics

###Array ####Definition:

Stores data elements based on an sequential, most commonly 0 based, index.
Based on tuples from set theory.

	/**

	Good morning! Here's your coding interview problem for today.

	This problem was asked by Yahoo.

	Recall that a full binary tree is one in which each node is either a leaf node, or has two children. Given a binary tree, convert it to a full one by removing nodes with only one child.

	For example, given the following tree:

	import java.util.Arrays;

	/**
	* quickselect is a selection algorithm to find the kth smallest element in an
	* unordered list. Like quicksort, it is efficient in practice and has good
	* average-case performance, but has poor worst-case performance. Quickselect
	* and variants is the selection algorithm most often used in efficient
	* real-world implementations.
	*
	* Quickselect uses the same overall approach as quicksort, choosing one

	import java.util.Arrays;

	/**
	* Given an array of n integers nums and a target, find the number of index triplets i, j, k with 0 <= i < j < k < n
	* that satisfy the condition nums[i] + nums[j] + nums[k] < target.
	* <p>
	* For example, given nums = [-2, 0, 1, 3], and target = 2.
	* Return 2. Because there are two triplets which sums are less than 2:
	* <p>
	* [-2, 0, 1]

	/**
	Design and implement a TwoSum class. It should support the following operations: add and find.

	add - Add the number to an internal data structure. find - Find if there exists any pair of numbers which sum is equal to the value.

	For example,
	add(1); add(3); add(5);
	find(4) -> true
	find(7) -> false
	**/

	/* package whatever; // don't place package name! */

	import java.util.*;
	import java.lang.*;
	import java.io.*;

	/* Name of the class has to be "Main" only if the class is public. */
	class Ideone
	{
	public static void main (String[] args) throws java.lang.Exception

	public List<Integer> spiralOrder(List<ArrayList<Integer>> a){

	if( a == null \|\| a.isEmpty()) {
	return null;
	}
	// base case 3x3 then tweak
	int startRow = 0;
	int startCol = 0;

	int endRow= a.size();

	public static void main (String... args){

	UUID uid = UUIDs.timeBased();
	long time = getTimeFromUUID(uid);
	Date date = new Date(time);
	System.out.println(date);
	}

	static final long NUM_100NS_INTERVALS_SINCE_UUID_EPOCH = 0x01b21dd213814000L;
	public static long getTimeFromUUID(UUID uuid) {


	public class Singleton
	{
	private Singleton singleton;

	//make the constructor protected- to defeat instantiation.
	protected Singleton(){}

	public static Singleton getInstance() {
	if(singleton == null) {

	/**
	* Convert from Postfix to Infix Notation
	* Infix to Postfix :https://gist.github.com/KodeSeeker/f776c5477c3be3f43a77
	* Algo:
	* 1) Walk through postfix expression
	* 2) If input is a num then push to stack.
	* 3) If the input is a operator then pop the last two operatonds from stack and perform operation. Push result back onto stack.
	*
	* Error condition : if you see a operator and there arent 2 operands in the left in the stack.
	*