Q: Check whether if a string has all Unique characters. Follow-Up : What if extra space is NOT provided for solving the problem i.e. E(Space) = O(1). Two methods are used . Method1 - Simple one which is composed for alphabetic inputs alone Method2 - Depth one which is done for characters having decimal value from 32 to 127 ie., It includes all possible characters. It can also be designed even for sentences or paragraphs by modifying the data type.