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.


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.


The first line contains one integer, which is the desired minimal number.




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Santiago Palacio: 2011-05-30 02:23:26

Does the Case matters (a != A) ?

Last edit: 2011-05-30 02:23:47
pankaj: 2011-05-27 07:46:28

reduction of problem is needed.

Nikhil Garg: 2010-08-18 07:00:13

Try optimizing on space. ;-)

Ravi Kiran: 2010-08-16 19:34:03

O(N^2) with optimisations can pass.
Also try AIBOHP first.

Last edit: 2010-08-16 19:42:41

Added by:Gareev
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