Roger7410’s gists

Roger7410 / 234PalindromeLinked List.java

Created October 15, 2016 01:32

	public class Solution {

	public boolean isPalindrome(ListNode head) {
	if(head == null \|\| head.next == null) return true;

	ListNode slow = head, fast = head;
	ListNode cur = head, rev = null;

	//Finding mid point with fast slow, while also reversing first half
	while(fast != null && fast.next != null){

Roger7410 / 49Group Anagrams.java

Created October 14, 2016 00:04

	public class Solution {
	public List<List<String>> groupAnagrams(String[] strs) {
	if(strs.length < 1 \|\| strs == null) return new ArrayList<List<String>>();
	Map<String,List<String>> map = new HashMap<>();
	for(String s: strs){
	char[] chars = s.toCharArray();
	Arrays.sort(chars);
	String key = String.valueOf(chars);
	if(!map.containsKey(key)) map.put(key, new ArrayList<String>());
	map.get(key).add(s);

Roger7410 / 290Word Pattern.java

Created October 13, 2016 22:45

	public class Solution {
	public boolean wordPattern(String pattern, String str) {
	String[] arr= str.split(" ");
	HashMap<Character, String> map = new HashMap<Character, String>();
	if(arr.length!= pattern.length())
	return false;
	for(int i=0; i<arr.length; i++){
	char c = pattern.charAt(i);
	if(map.containsKey(c)){
	if(!map.get(c).equals(arr[i]))

Roger7410 / 389.Find the Difference.java

Created October 13, 2016 22:38

	//It is a more effictive way than HASHTABLE
	public class Solution {
	public char findTheDifference(String s, String t) {
	char[] ss = s.toCharArray();
	char[] tt = t.toCharArray();
	char result = 0;
	for(int i = 0; i <ss.length; i++){
	result ^= ss[i];
	result ^= tt[i];
	}

Roger7410 / 103. Binary Tree Zigzag Level Order Traversal.java

Created October 12, 2016 22:38

	public class Solution {
	public List<List<Integer>> zigzagLevelOrder(TreeNode root) {
	List<List<Integer>> res = new ArrayList<List<Integer>>();
	if(root == null) return res;
	Queue<TreeNode> queue = new LinkedList<>();
	queue.add(root);
	boolean order = true;
	while(!queue.isEmpty()){
	int size = queue.size();
	List<Integer> tmpList = new ArrayList<>();

Roger7410 / 102. Binary Tree Level Order Traversal.java

Created October 12, 2016 21:53

	public class Solution {
	// public List<List<Integer>> levelOrder(TreeNode root) {
	// List<List<Integer>> result = new ArrayList<>();
	// Queue<TreeNode> queue = new LinkedList<>();
	// if(root == null) return result;
	// queue.add(root);
	// while(!queue.isEmpty()){
	// int size = queue.size();
	// List<Integer> tmpList = new ArrayList<>();
	// for(int i=0; i<size; i++){

Roger7410 / 111. Minimum Depth of Binary Tree.java

Created October 12, 2016 21:49

	public class Solution {
	int min = Integer.MAX_VALUE;
	int count = 0;
	public int minDepth(TreeNode root) {
	if(root!=null){
	count++;
	if(root.left==null && root.right==null){
	if(count < min) min = count;
	}else{
	minDepth(root.left);

Roger7410 / 104 Maximum Depth of Binary Tree

Created October 12, 2016 21:43

	/**
	* Definition for a binary tree node.
	* public class TreeNode {
	* int val;
	* TreeNode left;
	* TreeNode right;
	* TreeNode(int x) { val = x; }
	* }
	*/
	public class Solution {

Roger7410 / 3SumCloset_OCT11.java

Created October 12, 2016 04:59

	public class Solution {
	public int threeSumClosest(int[] nums, int target) {
	//each input would have exactly one solution
	int result = 0;
	Arrays.sort(nums);
	//i j k are indexs
	int i = 0;
	int minCloset = Integer.MAX_VALUE;
	while(i < nums.length - 2){
	int j = i + 1;

Roger7410 / 3Sum_OCT11.java

Last active October 12, 2016 00:56

	//haha
	class Solution{
	public List<List<Integer>> threeSum(int[] nums){
	List<List<Integer>> results = new ArrayList<>();
	if(nums.length < 3) return results;
	Arrays.sort(nums);
	//i j k are indexs
	int i = 0;
	while(i < nums.length - 2){
	if(nums[i]>0) break;

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