Flood Fill Algorithm

The flood fill problem is a way to fill a region of connected pixels with a new colour, starting from a given pixel in an image. You are given an image represented by an m x n grid of integers, where the image[i] represents the pixel value at position (i, j). You are also given the coordinates of a starting pixel (x, y) and a new colour to use for the flood fill operation.

Merge Two Binary Trees

Given two binary trees, write a program to merge them into a single binary tree. We need to merge them such that if two nodes overlap then add them and put them into the new tree at the same position. Otherwise, put the non-NULL node in the new tree. Note: This is an excellent problem to learn problem solving using iterative and recursive preorder traversal.

Height (Maximum Depth) of a Binary Tree

Given a binary tree, write a program to find its height. In other words, we are given a binary tree and we need to calculate the maximum depth of the binary tree. The height or maximum depth of a binary tree is the total number of edges on the longest path from the root node to the leaf node. Note: This is an excellent problem to learn problem-solving using DFS and BFS traversal.

Preorder, Inorder and Postorder Traversal using Recursion

There are three types of recursive tree traversals: preorder, inorder and postorder. This classification is based on the visit sequence of root node 1) Preorder traversal: root is visited first 2) Inorder traversal: root is visited after left subtree 3) Postorder traversal: root is visited last. These are also called depth first search or DFS traversal.

Validate Binary Search Tree (BST)

Given the root of a binary tree, write a program to check whether tree is a valid binary search tree (BST) or not. To check valid bst, we verify bst property at each node: All node values in the left subtree are less than node’s value, all node values in the right subtree are greater than node’s value, and both subtrees are also binary search trees.

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