SDE - 1

You are given a string (STR) of length N, consisting of only the lower case English alphabet.

Your task is to remove all the duplicate occurrences of characters in the string.

For Example:

If the given string is:
abcadeecfb

Then after deleting all duplicate occurrences, the string looks like this:
abcdef

You have been given a Binary Tree of 'n' nodes, where the nodes have integer values

Print the left view of the binary tree.

Example :

If the input tree is as depicted in the picture: 

The Left View of the tree will be:  2 35 2 

You and your friend found a string ‘S’ of length ‘N’. You love to rearrange the strings, So you decided to rearrange this string too. But this time, your friend puts a constraint on rearranging. He gave you ‘M’ pairs of integers, each pair denoting two indices of the string ‘S’. He also gave you an operation. In one operation, you can select a pair of indices from the given ‘M’ pairs and swap the character present at those indices in the string.

Your task is to rearrange the strings following the given constraints and find the lexicographically smallest string that you can obtain by doing the operations any number of times (might be 0 as well).

You are given a string 'str' of length 'N'.

Your task is to return the longest palindromic substring. If there are multiple strings, return any.

A substring is a contiguous segment of a string.

For example :

str = "ababc"

The longest palindromic substring of "ababc" is "aba", since "aba" is a palindrome and it is the longest substring of length 3 which is a palindrome. 

There is another palindromic substring of length 3 is "bab". Since starting index of "aba" is less than "bab", so "aba" is the answer.