Jeffwan

package CC150.ArraysAndString;

/**
 * Implement a function reverse which reverse a null-terminated string (null-terminated only works for C/C++)
 */
public class ReverseString {
	public static void main(String args[]) {
		System.out.println(reverse("hello"));
	}
	

Jeffwan

package CC150.ArraysAndString;
/**
 * I misunderstand the defination of permutation. I treat it as reverse.
 * Permutation means anyway, but reversed.  abb is a permutation of bab.  
 * Permutation feature: the count of ever number is same, any combination is valid 
 */
public class Permutation {

	public static void main(String[] args) {
		System.out.println(permutation("fabcdfedfaaa","abacdaedfaff"));

Jeffwan

package CC150.ArraysAndString;

/**
 * 1. Calculate spaces count first, then we know new char[] length 
 * 2. To prevent overlap, start replace from end to head
 *
 * true length < str.length because of input may end with many spaces.
 * length = str.length - end spaces
 * 
 * book use newLength - 1, then newLength--, I use step here.

Jeffwan

package leetcode;

import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

/**

Jeffwan

package CC150.ArraysAndString;

/**
 * Check if s2 is a rotation of s1 using only one call to isSubstring
 * eg: "waterbottle" is a rotation of "erbottlewat" 
 *
 */
public class IsRotation {

	public boolean isRotation2(String s1, String s2) {

Jeffwan

package leetcode.combinations;
import java.util.ArrayList;


public class Combine {
	public static void main(String args[]) {
		System.out.println(combine(4,2));
	}
	
	/**

Jeffwan

package leetcode.simpleCoding;

/**
 * @author jeffwan
 * @date Feb 8, 2014
 * 
 * Objective: write the simple and readable codes
 * There's no algorithm in this kind of problem but some tiny simple method. Our goal is to make it as clear as possible. 
 * In addition, It's a good opportunity communicatting with interviewer about the overflow, 100 -- 001 (display). 
 * 

Jeffwan

package leetcode.simpleCoding;

/**
 * @date Feb 8, 2014
 * 
 * Test case:  (1123 123)  ("","") --> may OutOfBound ,("a","a") --> s1.length()- s2.length()+1 not without +1, bound check. 
 * return value: haystack.subString(i) but not String.valueOf(i) ("","" will return 0).
 * take care 
 */
public class StrStr {

Jeffwan

package leetcode.tree;

import java.util.ArrayList;
import java.util.Stack;

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;

Jeffwan

package leetcode.tree;

import java.util.ArrayList;
import java.util.Stack;

import leetcode.tree.InorderTraversal.TreeNode;

public class PreorderTraversal {

	public ArrayList<Integer> preorderTraversal(TreeNode root) {