1. given a binary tree, print the preorder traversal in recursive and iterative way
2. Reverse words in a given string
3. people are standing in a queue when viewed from the front, m heads are visible, and n heads from the end. Find the number of possible arrangements such that m&n remains same when viewed from front and end respectively.
2. What is the minimum number of straight lines to connect all the dots on this grid?
1. Design a data structure for updating an object efficiently in a multithreaded environment. (critical section problem)
2. Singleton Design pattern.
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