SDE - 1

You have been given the preorder and inorder traversal of a binary tree. Your task is to construct a binary tree using the given inorder and preorder traversals.

Note:

You may assume that duplicates do not exist in the given traversals.

For example :

For the preorder sequence = [1, 2, 4, 7, 3] and the inorder sequence = [4, 2, 7, 1, 3], we get the following binary tree.

You are given a list of ‘transactions’ between ‘n’ number of friends. who have to give each other money. The list consists of data of receiver, sender, and transaction.

Your task is to minimize the cash flow and the total number of transactions should also be minimum.

For example :

In figure 1 : friend-1 has to pay 2000$ to friend-2, and 4000$ to friend-3 and friend-2 has to pay 3000$ to friend-3.

In figure 2 : so we can minimize the flow between friend-1 to friend-2 by direct pay to friend-1 to friend-3

You are given a positive integer 'N'. Your task is to find the number of strings of length ‘N’ that can be formed using only the characters ‘a’, ‘b’ and ‘c’. The strings formed should be such that the number of ‘b’ and ‘c’ in the string is at most 1 and 2, respectively.

Example:

Let’s say N = 2. The strings of length 2, which satisfy the given constraints are: “aa”, “ab”, “ac”, “ba”, “bc”, “ca”, “cb”, “cc”. Hence, the output is 8.

Ninja is learning tree data structure these days. While learning, she came across learn about the Binary Search tree. She found BST quite interesting. She decided to make her own Binary Search Tree. Being a newbie, she made a mistake and swap two nodes of the Binary Search Tree.

Your responsibility being an expert and a good friend is to correct the Binary Search Tree made by Ninja and recover the correct Binary Search Tree.

A binary search tree (BST) is a binary tree data structure with the following properties.

• The left subtree of a node contains only nodes with data less than the node’s data.
• The right subtree of a node contains only nodes with data greater than the node’s data.
• Both the left and right subtrees must also be binary search trees.

Example

This is the binary search tree made by Ninja. But here, the left node of 8 is greater, and the right node is smaller.
If we swap the right and the left node of 8 Ninja’s Binary Search Tree will become correct.

This is the correct binary Search Tree.

You are given the schedule of 'N' meetings with their start time 'Start[i]' and end time 'End[i]'.

You have only 1 meeting room. So, you need to return the maximum number of meetings you can organize.

Note:

The start time of one chosen meeting can’t be equal to the end time of the other chosen meeting.

For example:

'N' = 3, Start = [1, 3, 6], End = [4, 8, 7].

You can organize a maximum of 2 meetings. Meeting number 1 from 1 to 4, Meeting number 3 from 6 to 7.