zac-xin

/*
 * print a binary tree in level order using DFS & BFS
 */
package Chapter4;

import java.util.Queue;
import java.util.LinkedList;

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

zac-xin

/*
 * find lowest common ancestor in a Binary Tree
 */
package Chapter4;

public class FindLCA_2 {
    public static void main(String args[]){
        TreeNode n1 = new TreeNode(22, null, null);
        TreeNode n2 = new TreeNode(2, n1, null);
        TreeNode n4 = new TreeNode(4, null, null);

zac-xin

/*
 * find lowest common ancestor in a Binary Search Tree(BST)
 */
package Chapter4;

public class FindLCA_1 {
    public static void main(String args[]){
        TreeNode n1 = new TreeNode(1, null, null);
        TreeNode n2 = new TreeNode(2, n1, null);
        TreeNode n4 = new TreeNode(4, null, null);

zac-xin

public class Solution {
    public int uniquePaths(int m, int n) {
        int matrix[][] = new int[m + 1][n + 1];
        
        return backtrack(matrix, 0 , 0, m, n);
    }
    
    public int backtrack(int[][] matrix, int c, int r, int m, int n){
        if(c == m - 1 && r == n -1){
            return 1;

zac-xin

public class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        
        int matrix[][] = new int[m][n];
        
        for(int i = n - 1; i >= 0; i--){

zac-xin

/*
 * build tree from inorder and preorder
 */
package Chapter4;

public class BuildTree {
    public static void main(String args[]){
        int pre[] = {7, 10, 4, 3,1,2,8,11};
        int in[] = {4,10,3,1,7,11,8,2};
        TreeNode root =buildTree(pre, in);

zac-xin

import java.util.ArrayList;

public class Solution {
    public ArrayList<ArrayList<Integer>> permute(int[] num) {
        return permuteRecursive(num, 0);   
    }
    
    public ArrayList<ArrayList<Integer>> permuteRecursive(int[] num, int index){
        if(index == num.length - 1){
            ArrayList<Integer> list = new ArrayList<Integer>();

zac-xin

package Chapter2;
/*
 * reverse a linked list
 */
public class ReverseList {
    public static void main(String args[]){
        IntNode n1, n2, n3, n4, n5, n6,n7, n8, n9;
        n9 = new IntNode(10, null);
        n8 = new IntNode(9, n9);
        n7 = new IntNode(8, n8);

zac-xin

package Chapter9;
/*
 * 9-6 Given a matrix in which each row and each column is sorted,
 *  write a method to find an element in it.
 */
public class Question9_6 {
    public static void main(String args[]){
        int m[][]= {
                {1,4,5,6,8},
                {2,5,7,8,10},

zac-xin

/*
 * Given a sorted array of strings which is interspersed with empty strings, 
 * write a meth- od to find the location of a given string.
    Example: find “ball” in [“at”, “”, “”, “”, “ball”, “”, “”, “car”, “”, “”, “dad”, “”, “”] 
    will return 4 
    Example: find “ballcar” in [“at”, “”, “”, “”, “”, “ball”, “car”, “”, “”, “dad”, “”, “”] 
    will return -1
 */
package Chapter9;