SDE - 1

You are given an integer array 'ARR' of size 'N' and an integer 'S'. Your task is to return the list of all pairs of elements such that each sum of elements of each pair equals 'S'.

Note:

Each pair should be sorted i.e the first value should be less than or equals to the second value. 

Return the list of pairs sorted in non-decreasing order of their first value. In case if two pairs have the same first value, the pair with a smaller second value should come first.

You are given a sorted integer array 'arr' of size 'n'.

You need to remove the duplicates from the array such that each element appears only once.

Return the length of this new array.

Note:

Do not allocate extra space for another array. You need to do this by modifying the given input array in place with O(1) extra memory. 

For example:

'n' = 5, 'arr' = [1 2 2 2 3].
The new array will be [1 2 3].
So our answer is 3.

Given a singly linked list of 'N' nodes. The objective is to determine the middle node of a singly linked list. However, if the list has an even number of nodes, we return the second middle node.

Note:

1. If the list is empty, the function immediately returns None because there is no middle node to find.
2. If the list has only one node, then the only node in the list is trivially the middle node, and the function returns that node.

Suppose that you are trapped on the surface of a frozen lake. The surface is so smooth and ideal that there is no friction at all. You cant make any grip on the ice and no wind is blowing to help you out. You have just a mobile phone with you which has got no reception disabling you to call for help. How will you plan your escape before you freeze to death on the frozen lake?