Given an array of integers and a value.Which array index will give maximum result after XORing with the given value. How can we find that efficiently?

You are getting a stream of characters and at any time you can be asked to find out if the string received yet is palindrome or not. There can be multiple queries.He insisted to do it in better than O(n) and No extra space.

Power Tower Problem-

Given two power towers, find out which one is larger. Power tower is a number of the form : a1 ^ ( a2 ^ (a3 ^ (.... ^an)

You can assume that N <= 100, and each ai <= 100.
I don't have any efficient solution yet.

Source:
A sub-task in ICPC world finals 2012

determine whether the given string is of form pZq where q is reverse of q. p and q can contain only X and Y.

like if p=XXYX then z will be XYXX
for ex XXYXXXYXX is valid

the constraints is that "you can read only the next character at each point" .

You are given a string of ‘n’ characters where n is even. The string only consist of 6 type of characters: (){}[]. The task is to form a well formed expression. A well formed expression consist of proper nesting of braces and their is no priority between the braces like [ > } > ). You can edit any bracket and change it to remaining types for accomplishing the task.

Example A. "(){}" is valid B. "({[]})” is valid C. “((})” is invalid

Given a BST, convert it so that each node has value equal to sum of all the nodes (including itself) which are greater than that node in the whole tree.

You are given a positive integer A. The goal is to construct the shortest possible sequence of integers ending with A, using the following rules

the first element of the sequence is 1,each of the successive elements is the sum of any two preceding elements (adding a single element to itself is also permissible),
each element is larger than all the preceding elements; that is, the sequence is increasing.

For example, for A = 42, a possible solutions is [1, 2, 3, 6, 12, 24, 30, 42]. Another possible solution is [1, 2, 4, 5, 8, 16, 21, 42].