Today we will discuss a popular interview question. The problem tests a developers hands-on on various aspect of Java programming language as well as his problem solving ability. The resultant solution must have optimum time and space complexity. Problem Statement: Find the root of largest tree in the forest. Given each tree is represented as a hashmap entry with child as the key and parent as the value. Higher the number of children for any given root larger the tree. constrains: a. One child has only one immediate parent b. Any parent can have more than one children c. If two trees are equal then return root with least id Sample forest: {{1 -> 2}{3 -> 4}} Here we have 2 trees, one with node 1 and root 2 and second with node 3 and root 4. Both trees have same size hence the output should be the node with least id ie. 2. Solution: Approach: We receive input hashmap with key as child and value as parent, hence child nodes are unique in this collection but parent values can b...