Form a palindrome

Solution of geeksforgeeks problem.
http://practice.geeksforgeeks.org/problems/form-a-palindrome/0

Problem:
Given a string, find the minimum number of characters to be inserted to convert it to palindrome.

For Example:
ab: Number of insertions required is 1. bab or aba
aa: Number of insertions required is 0. aa
abcd: Number of insertions required is 3. dcbabcd

Preorder to Postorder

Recursive solution to a problem of geeksforgeeks.
http://practice.geeksforgeeks.org/problems/preorder-to-postorder/0

Problem:
Given an array representing preorder traversal of BST, print its postorder traversal.