jingz8804

import java.util.Arrays;
public class Search2DMatrix{
    public boolean searchMatrixOne(int[][] matrix, int target){
        int numOfRows = matrix.length;
        int numOfColumns = matrix[0].length;
        
        if (numOfRows == 0 || numOfColumns == 0) return false;
        
        // here we assume that the total number of elements in the matrix 
        // is inside the range of Integer in Java

jingz8804

public class StockOne{
    // example: [5, 4, 1, 2, 8, 6, 9]
    public int maxProfit(int[] prices){
        if(prices.length <= 1) return 0;
        return maxProfitOne(prices);
        // return maxProfitTwo(prices, 0, prices[0], 0);
        // return maxProfitThree(prices, new Integer(-1), 0);
    }
    
    // this function use the iterative algorithm

jingz8804

import java.util.Iterator;
import java.util.NoSuchElementException;

public class Deque<Item> implements Iterable<Item>{
    private Item[] deck; // the array for the deck
    private int N; // the number of items in the deck
    private int head;
    private int tail;
    
    public Deque(){

jingz8804

// in this context, we've already know that the list has cycle
// suppose there is a class Node 
// public class Node<Item>{
//     Item item;
//     Node next;
// }
// import the Node class here;
public class DetectCycleStartInList{// I wish I could use a better name :)
    
    

jingz8804

import java.util.Hashtable;
public class CloneDoubleLinkedList{
    private class Node{
        private String item;
        private Node next;
        private Node random;
    }
    
    public Node cloneListClever(Node first){
        Node current = first;

jingz8804

import java.util.Stack;
public class SimplifyPath {
    public String simplifyPath(String path) {
        if(path == null) return null;
        Stack<String> s = new Stack<String>();
        int len = path.length();
        StringBuilder b = new StringBuilder();
        String item = null;
        for (int i = 1; i < len; i++){ // start with the char at index 1 since the first is always '/'
            char c = path.charAt(i);

jingz8804

import java.util.Stack;
import java.util.LinkedList;

public class SymmetricTree {
    public boolean isSymmetricQueue(TreeNode root) {
        if (root == null) return true; // if you say so
        
        // initialize a queue since we are going to use breadth first traverse
        LinkedList<TreeNode> q = new LinkedList<TreeNode>();
        if (root.left !=null && root.right != null) {

jingz8804

import java.util.Random;

public class RandomItem{
    private int[] numbers;
    private double[] probs;
    private Random rand;
    
    public RandomItem(int[] numbers, double[] probs){
        this.numbers = numbers;
        this.probs = probs;

jingz8804

import java.util.Stack;
public class Evaluate{
    private Stack<Double> operands;
    private Stack<String> operators;
    
    public Evaluate(){
        operands = new Stack<Double>();
        operators = new Stack<String>();
    }
    

jingz8804

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }