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.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;
 *     }
 * }

jingz8804

public class ZigZagConversion {
    public String convert(String s, int nRows) {
        // corner cases
        if(s == null) return null;
        if(s.equals("")) return s;
        if(nRows == 0) return null;
        if(nRows == 1) return s;
        
        StringBuilder[] builders = new StringBuilder[nRows];
        for(int i = 0; i < nRows; i++){

jingz8804

import java.util.ArrayList;
public class SpiralMatrix {
    public ArrayList<Integer> spiralOrder(int[][] matrix) {
		if (matrix == null)
			return null;
		if (matrix.length == 0)
			return new ArrayList<Integer>(); // ask first
		int nrows = matrix.length;
		int ncols = matrix[0].length;

jingz8804

public class SetMatrixZeros {
    public void setZeroes(int[][] matrix) {
        if(matrix == null) return;
        if(matrix.length == 0) return;
        
        int m = matrix.length;
        int n = matrix[0].length;
        
        boolean[] rows = new boolean[m];
        boolean[] cols = new boolean[n];

jingz8804

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
import java.util.Stack;