zac-xin

public class TestUnique {

	/* use a array to record the occurrence of different characters
	 * first method uses extra space
	 * NOTE: the spaces will cause duplicates too
	 * the time complexity is O(n), the space complexity is also O(n)
	 */
	public static boolean test(String input){
		boolean char_set[] = new boolean[255]; 
		

zac-xin

public class StringReverse {
	public static void main(String args[]){
		String s = "this is a demo test!";
		System.out.println(reverse(s));
	}
	
	public static String reverse(String input){
		char[] data = input.toCharArray();
		int i = 0;
		int j = data.length - 1;

zac-xin

public class RemoveDuplicates {
	public static void main(String args[]){
		String s = "1234512345aabbbccccddddddeeefffffggg";
		char[] input = s.toCharArray();
		removeDup(input);
		System.out.println(input);
	}
	
	public static void removeDup(char[] data){
		int len = data.length;

zac-xin

public class TestAnagram {
	public static void main(String args[]){
		String a = "tomcat  as";
		String b = " tamcots a";
		System.out.println(test(a, b));
	}
	
	public static boolean test(String s1, String s2){
		if(s1.length() != s2.length())
			return false;

zac-xin

public class ReplaceSpace {
	public static void main(String args[]){
		System.out.println(replaceSpace("this is a demo test! "));
	}
	
	public static String replaceSpace(String input){
		char s[] = input.toCharArray();
		int spaceCount = 0;
		int index = 0;
		

zac-xin

public class RotateMatrix {
	public static void main(String args[]){
		int[][] matrix = {
				{1, 2, 3 ,4 ,5 ,6},
				{12, 13, 14, 15, 16, 17},
				{23, 24, 25, 26, 27, 28},
				{34, 35, 36, 37, 38, 39},
				{45, 46, 47, 48, 49, 50},
				{66, 67, 68, 69, 70, 71}
		};

zac-xin

public class SetZero {
	public static void main(String args[]){
		int[][] matrix = {
				{1, 2, 3 ,4 ,5 ,6},
				{12, 13, 0, 15, 16, 17},
				{23, 24, 25, 26, 27, 28},
				{34, 35, 36, 0, 38, 39},
				{45, 46, 47, 48, 49, 50},
				{66, 0, 68, 69, 1, 71},
				{33, 46, 47, 48, 49, 50}

zac-xin

/*
 * Assume you have a method isSubstring which checks if one word is a substring of 
 * another.
 * Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 using 
 * only one call to isSubstring (i e , “waterbottle” is a rotation of “erbottlewat”) 
 */

public class SubString {
	public static void main(String args[]){

zac-xin

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


/*
 *  A LinkedList class with a private static inner node class
 * 	based on: 
 *  http://www.cs.cmu.edu/~adamchik/15-121/lectures/Linked%20Lists/linked%20lists.html
 *  

zac-xin

        public AnyType findLastNth(int k){
		if(head == null || k <= 0)
			return null;
		if(size() < k)
			return null;
		
		Node<AnyType> tmp = head;
		for(int i = 0; i < k; i++)
			tmp = tmp.next;