Introduction

In this blog post, we'll share the most commonly asked coding interview questions at josh technology. If you don't have months to study for your interviews, you can use AI tools like Chatmagic to generate solutions quickly and efficiently - helping you pass the interviews and get the job offer!

Problem #1: Move Zeroes

Given an integer array nums, move all 0's to the end of it while maintaining the relative order of the non-zero elements. Note that you must do this in-place without making a copy of the array. Example 1: Input: nums = [0,1,0,3,12] Output: [1,3,12,0,0] Example 2: Input: nums = [0] Output: [0] Constraints: 1 <= nums.length <= 104 -231 <= nums[i] <= 231 - 1 Follow up: Could you minimize the total number of operations done?

Topics: Array, Two Pointers

Problem #2: Reverse Odd Levels of Binary Tree

Given the root of a perfect binary tree, reverse the node values at each odd level of the tree. For example, suppose the node values at level 3 are [2,1,3,4,7,11,29,18], then it should become [18,29,11,7,4,3,1,2]. Return the root of the reversed tree. A binary tree is perfect if all parent nodes have two children and all leaves are on the same level. The level of a node is the number of edges along the path between it and the root node. Example 1: Input: root = [2,3,5,8,13,21,34] Output: [2,5,3,8,13,21,34] Explanation: The tree has only one odd level. The nodes at level 1 are 3, 5 respectively, which are reversed and become 5, 3. Example 2: Input: root = [7,13,11] Output: [7,11,13] Explanation: The nodes at level 1 are 13, 11, which are reversed and become 11, 13. Example 3: Input: root = [0,1,2,0,0,0,0,1,1,1,1,2,2,2,2] Output: [0,2,1,0,0,0,0,2,2,2,2,1,1,1,1] Explanation: The odd levels have non-zero values. The nodes at level 1 were 1, 2, and are 2, 1 after the reversal. The nodes at level 3 were 1, 1, 1, 1, 2, 2, 2, 2, and are 2, 2, 2, 2, 1, 1, 1, 1 after the reversal. Constraints: The number of nodes in the tree is in the range [1, 214]. 0 <= Node.val <= 105 root is a perfect binary tree.

Topics: Tree, Depth-First Search, Breadth-First Search, Binary Tree

Problem #3: Find Bottom Left Tree Value

Given the root of a binary tree, return the leftmost value in the last row of the tree. Example 1: Input: root = [2,1,3] Output: 1 Example 2: Input: root = [1,2,3,4,null,5,6,null,null,7] Output: 7 Constraints: The number of nodes in the tree is in the range [1, 104]. -231 <= Node.val <= 231 - 1

Topics: Tree, Depth-First Search, Breadth-First Search, Binary Tree

Problem #4: Count Good Nodes in Binary Tree

Given a binary tree root, a node X in the tree is named good if in the path from root to X there are no nodes with a value greater than X. Return the number of good nodes in the binary tree. Example 1:
Input: root = [3,1,4,3,null,1,5] Output: 4 Explanation: Nodes in blue are good. Root Node (3) is always a good node. Node 4 -> (3,4) is the maximum value in the path starting from the root. Node 5 -> (3,4,5) is the maximum value in the path Node 3 -> (3,1,3) is the maximum value in the path. Example 2:
Input: root = [3,3,null,4,2] Output: 3 Explanation: Node 2 -> (3, 3, 2) is not good, because "3" is higher than it. Example 3: Input: root = [1] Output: 1 Explanation: Root is considered as good. Constraints: The number of nodes in the binary tree is in the range [1, 10^5]. Each node's value is between [-10^4, 10^4].

Topics: Tree, Depth-First Search, Breadth-First Search, Binary Tree

Problem #5: Maximum Twin Sum of a Linked List

In a linked list of size n, where n is even, the ith node (0-indexed) of the linked list is known as the twin of the (n-1-i)th node, if 0 <= i <= (n / 2) - 1. For example, if n = 4, then node 0 is the twin of node 3, and node 1 is the twin of node 2. These are the only nodes with twins for n = 4. The twin sum is defined as the sum of a node and its twin. Given the head of a linked list with even length, return the maximum twin sum of the linked list. Example 1: Input: head = [5,4,2,1] Output: 6 Explanation: Nodes 0 and 1 are the twins of nodes 3 and 2, respectively. All have twin sum = 6. There are no other nodes with twins in the linked list. Thus, the maximum twin sum of the linked list is 6. Example 2: Input: head = [4,2,2,3] Output: 7 Explanation: The nodes with twins present in this linked list are: - Node 0 is the twin of node 3 having a twin sum of 4 + 3 = 7. - Node 1 is the twin of node 2 having a twin sum of 2 + 2 = 4. Thus, the maximum twin sum of the linked list is max(7, 4) = 7. Example 3: Input: head = [1,100000] Output: 100001 Explanation: There is only one node with a twin in the linked list having twin sum of 1 + 100000 = 100001. Constraints: The number of nodes in the list is an even integer in the range [2, 105]. 1 <= Node.val <= 105

Topics: Linked List, Two Pointers, Stack