Software Engineer

1. Sort the vector(non-decreasing).
2. First remove all the duplicates from vector.
3. Then use recursion and backtracking to solve 
the problem.

I used regular mathematucal vertical multiplication.
We loop from the end of both numbers, multiply the digits one at a time and save the carry in the next cell for the next iteration.
The loop at the end constructs the result string - we skip 0s at the beginning and add the numbers.

Tip 1: Revise your OS basics.
Tip 2: Threads are a way for a program to split itself into two or more simultaneously (or pseudo-simultaneously) running tasks. Deadlocks occur when two or more threads are blocked forever, waiting for each other.
Tip 3: Preventive measures for deadlocks include:
Avoiding the "hold and wait" situation by acquiring all the required resources at once, instead of waiting and acquiring them one by one.
Using "lock-ordering" to avoid a circular-wait situation.
Using a "time-out" mechanism to prevent threads from waiting indefinitely.
Using a "watchdog" thread that periodically checks for and resolves deadlocks.
Avoiding nested locks, where a thread holds a lock while trying to acquire another lock.
Using a non-blocking algorithm to avoid the need for locks altogether.
Use libraries or frameworks that provide deadlock prevention mechanisms.

The basic idea is to start with an empty list of permutations and recursively add elements from the input array to the list, while keeping track of the remaining elements that have not yet been used.
Another approach is to use backtracking algorithm, which follows the same idea of recursion but it is slightly different in implementation and it is more efficient than the recursive approach as it avoid recomputation.

Tip 1: A class is a blueprint or template for creating objects
Tip 2: An object is an instance of a class. It has the properties and methods defined by the class, but with specific values assigned to those properties
Tip 3:We need classes and objects because they provide a way to organize and structure code, making it more modular and reusable

Tip 1: Quicksort is preferred for arrays because it is an in-place sorting algorithm, meaning that it does not require additional memory space to sort the array.
Tip 2: merge sort is preferred for linked lists because of its efficient merging strategy and not requiring extra memory space.

Tip 1: To print the left view of a binary tree, we can use a level-order traversal (also known as breadth-first search) of the tree. 
Tip 2: The idea is to traverse the tree level by level, starting from the root, and print the first node of each level.