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Commit 86e0d8d

Browse files
Added some more Medium questions 🚀
1 parent 5f99578 commit 86e0d8d

24 files changed

+456
-8
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/**
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* Definition for a binary tree node.
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* public class TreeNode {
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* int val;
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* TreeNode left;
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* TreeNode right;
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* TreeNode(int x) { val = x; }
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* }
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*/
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class Solution {
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public List<Integer> inorderTraversal(TreeNode root) {
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List<Integer> list = new ArrayList<>();
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Stack<TreeNode> stack = new Stack<TreeNode>();
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TreeNode node = root;
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while (node != null || !stack.isEmpty())
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{
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if (node != null)
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{
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stack.push(node);
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node = node.left;
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}
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else
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{
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node = stack.pop();
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list.add(node.val);
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node = node.right;
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}
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}
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return list;
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}
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}
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import java.util.*;
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class TreeNode {
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int val;
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TreeNode left;
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TreeNode right;
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TreeNode(int x) { val = x; }
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}
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class Solution {
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public List<List<Integer>> levelOrder(TreeNode root) {
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List<List<Integer>> res = new ArrayList<>();
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if (root == null) return res;
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Queue<TreeNode> queue = new LinkedList<>();
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queue.add(root);
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while (!queue.isEmpty()) {
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List<Integer> level = new ArrayList<>();
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int size = queue.size();
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for (int i = 0; i < size; i++) {
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TreeNode node = queue.poll(); //Returns & Del element from front
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level.add(node.val); //Add to the List
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if (node.left != null) {
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queue.add(node.left);
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}
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if (node.right != null) {
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queue.add(node.right);
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}
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}
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res.add(level);
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}
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return res;
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}
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/* ANOTHER METHOD USING DFS */
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public List<List<Integer>> levelOrder2(TreeNode root) {
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List<List<Integer>> res = new ArrayList<List<Integer>>();
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levelHelper(res, root, 0);
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return res;
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}
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public void levelHelper(List<List<Integer>> res, TreeNode root, int height) {
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if (root == null) return;
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if (height >= res.size()) {
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res.add(new LinkedList<Integer>());
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}
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res.get(height).add(root.val);
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levelHelper(res, root.left, height+1);
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levelHelper(res, root.right, height+1);
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}
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}
File renamed without changes.

‎Medium/DecodingWays.java‎ renamed to ‎Medium/DecodeWays.java‎

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class DecodingWays {
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class DecodeWays {
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public static int numDecodings(String s) {
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‎Medium/FindTheDuplicateNumber.java‎

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class Solution {
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public int findDuplicate(int[] nums) {
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/* 1st Method
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Arrays.sort(nums);
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for (int i = 1; i < nums.length; i++) {
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if (nums[i] == nums[i-1]) {
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return nums[i];
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}
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}
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return -1; */
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/* 2nd Method
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Set<Integer> seen = new HashSet<Integer>();
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for (int num : nums) {
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if (seen.contains(num)) {
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return num;
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}
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seen.add(num);
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}
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return -1; */
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/* 3rd Method Efficient
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Find the intersection point of the two runners.
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int tortoise = nums[0];
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int hare = nums[0];
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do {
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tortoise = nums[tortoise];
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hare = nums[nums[hare]];
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} while (tortoise != hare);
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// Find the "entrance" to the cycle.
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int ptr1 = nums[0];
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int ptr2 = tortoise;
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while (ptr1 != ptr2) {
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ptr1 = nums[ptr1];
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ptr2 = nums[ptr2];
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}
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return ptr1;
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*/
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//Easy to Understand same as Hare Tortoise
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int slow = 0, fast = 0;
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do{
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slow = nums[slow];
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fast = nums[nums[fast]];
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}while(slow != fast);
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slow = 0;
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while(slow != fast){
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slow = nums[slow];
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fast = nums[fast];
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}
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return slow;
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}
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}

‎Medium/GenerateParentheses.java‎

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import java.util.*;
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class Solution {
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public List<String> generateParenthesis(int n) {
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List<String> list = new ArrayList<>();
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backtrack(list, "", 0, 0, n);
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return list;
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}
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public void backtrack(List<String> list, String cur, int open, int close, int max){
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if (cur.length() == max * 2) { //Eg max = 3
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list.add(cur); //If len becomes 6 add to List
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return;
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}
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if (open < max) //Add all the (((
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backtrack(list, cur+"(", open+1, close, max);
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if (close < open) //Add all the )))
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backtrack(list, cur+")", open, close+1, max);
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}
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}

‎Medium/GroupAnagrams.java‎

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import java.util.*;
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class Solution {
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public List<List<String>> groupAnagrams(String[] strs) {
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if (strs.length == 0) return new ArrayList<>();
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Map<String, List<String>> map = new HashMap<String, List<String>>();
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for (String s : strs) { //["eat", "tea", "tan", "ate", "nat", "bat"],
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char[] ca = s.toCharArray(); //will give [ e a t ]
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Arrays.sort(ca);
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String key = String.valueOf(ca);
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if (!map.containsKey(key)) //Add the sorted ie aet as key
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map.put(key, new ArrayList<>());
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map.get(key).add(s); //Add the original eat as Value in the key aet
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}
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return new ArrayList<>(map.values()); //Return all the values
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//Since we want to return List<List<String>>
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//Map.values() will return List<String> & Arraylist will return <List> of this List<String>
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}
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/* ANOTHER WAY OF DOING */
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public List<List<String>> groupAnagrams2(String[] strs) {
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Map<String, List<String>> map = new HashMap<>();
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for(String s: strs){
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int[] arr = new int[26];
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for(int i = 0;i<s.length();i++){
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arr[s.charAt(i) - 'a']++;
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}
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String key = Arrays.toString(arr);
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List<String> tempList = map.getOrDefault(key, new LinkedList<String>());
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tempList.add(s);
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map.put(key,tempList);
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}
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return new LinkedList<>(map.values());
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}
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}

‎Medium/GrumpyBookStoreOwner.java‎

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class GrumpyBookStoreOwner {
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class GrumpyBookstoreOwner {
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public int maxSatisfied(int[] customers, int[] grumpy, int X) {
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int sum = 0, maxWindow = 0, window = 0;

‎Medium/InOrderIterative.java‎

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import java.util.*;
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class TreeNode {
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int val;
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TreeNode left;
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TreeNode right;
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TreeNode(int x) { val = x; }
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}
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int val;
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TreeNode left;
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TreeNode right;
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TreeNode(int x) { val = x; }
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}
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class InOrderIterative {
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public List<Integer> inorderTraversal(TreeNode root) {

‎Medium/JumpGame.class‎

-967 Bytes
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