IOIPALIN  Palindrome 2000
A palindrome is a symmetrical string, that is, a string read identically from left to right as well as from right to left. You are to write a program which, given a string, determines the minimal number of characters to be inserted into the string in order to obtain a palindrome. As an example, by inserting 2 characters, the string "Ab3bd" can be transformed into a palindrome ("dAb3bAd" or "Adb3bdA"). However, inserting fewer than 2 characters does not produce a palindrome.
Input
The first line contains one integer: the length of the input string N, 3≤N≤5000. The second line contains one string with length N. The string is formed from uppercase letters from ‘A’ to ‘Z’, lowercase letters from ‘a’ to ‘z’ and digits from ‘0’ to ‘9’. Uppercase and lowercase letters are to be considered distinct.
Output
The first line contains one integer, which is the desired minimal number.
Example
Input: 5 Ab3bd Output: 2
hide comments
Santiago Palacio:
20110530 02:23:26
Does the Case matters (a != A) ? Last edit: 20110530 02:23:47 

pankaj:
20110527 07:46:28
reduction of problem is needed. 

Nikhil Garg:
20100818 07:00:13
Try optimizing on space. ;) 

Ravi Kiran:
20100816 19:34:03
O(N^2) with optimisations can pass.

Added by:  Gareev 
Date:  20100816 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: NODEJS OBJC PERL6 VB.NET 
Resource:  IOI 2000, Day 1 