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
raman_111: 2020-04-17 15:58:52

try once aibohphobia spoj dp problem
happy coding ;-)

igzou: 2020-03-10 08:20:53

Top down approach does not get time limit in cpp.

scolar_fuad: 2019-10-23 21:45:16

rought timelimit

adist98: 2019-07-16 05:03:29

It can be solved without LCS.

Last edit: 2019-07-16 21:14:58
exesharkx: 2019-03-26 22:45:16

reverse the String , calculate lcs of both string , print the Dif. length and lcs

foxtrot99: 2019-01-30 09:17:49

No Java solution passed till now :(

foxtrot99: 2019-01-30 09:15:55

Somehow, my most runtime and memory optimized code gets TLE in Java. Any suggestions?

the_root: 2018-12-03 20:40:49

pass in o(n^2)
hhhhhhhh but i have some WA because i forget start dp

elliot1: 2018-08-25 10:18:59

top down leads to TLE and bottom up works!! this is really weird -_-

one_piece_: 2018-07-10 05:22:27

@boris_dishov
min insertion required = n - (longest palindromic subsequence i.e. lcs of string 's' and reverse of string 's')
Here 'n' is length of string 's'

Last edit: 2018-07-10 05:22:55

Added by:Gareev
Date:2010-08-16
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