ANARC09A  Seinfeld
I’m out of stories. For years I’ve been writing stories, some rather silly, just to make simple problems look difficult and complex problems look easy. But, alas, not for this one.
You’re given a non empty string made in its entirety from opening and closing braces. Your task is to find the minimum number of “operations” needed to make the string stable. The definition for being stable is as follows:
 An empty string is stable.
 If S is stable, then {S} is also stable.
 If S and T are both stable, then ST (the concatenation of the two) is also stable.
All of these strings are stable: {}, {}{}, and {{}{}}; But none of these: }{, {{}{, nor {}{.
The only operation allowed on the string is to replace an opening brace with a closing brace, or visaversa.
Input
Your program will be tested on one or more data sets. Each data set is described on a single line. The line is a nonempty string of opening and closing braces and nothing else. No string has more than 2000 braces. All sequences are of even length.
The last line of the input is made of one or more ’’ (minus signs.)
Output
For each test case, print the following line:
k. N
Where k is the test case number (starting at one,) and N is the minimum number of operations needed to convert the given string into a balanced one.
Example
Input: }{
{}{}{}
{{{}

Output: 1. 2
2. 0
3. 1
hide comments
rockdude:
20111230 14:27:25
wat if there are odd no of { ,which can never be made stable by replacing with } or the lik... ?


Chandra Sekar:
20111230 14:27:25
yes! Sadly, DP solution gets TLE :( 

premanandh_j:
20111230 14:27:25
i used a stack with O(N) soln but got WA 

Kick:
20111230 14:27:25
Space between 1.<space>answer... Be careful 

Nguyen Khac Tung:
20111230 14:27:25
but if you're able to find a correct & fast greedy algo, it's better :D 

Ahmed Kamel [ahm.kam_92]:
20111230 14:27:25
Yes, i know that's there is a greedy O(N) solution, but dp should get AC like in the contest. 

Ambuj Varshney:
20111230 14:27:25
Think Carefully, a single iteration over each character of the string is sufficient for this question making it in O(N). 

Karim:
20111230 14:27:25
I am getting TLE too, i am doing O(N^2) DP solution. 

Ahmed Kamel [ahm.kam_92]:
20111230 14:27:25
Does dp solution gets TLE ? O(T*N^2)


[Trichromatic] XilinX:
20111230 14:27:25
Be careful with hidden '\r' at the end of each line... 
Added by:  Mohammad Kotb 
Date:  20091128 
Time limit:  3.236s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: ASM64 BASH JSRHINO 
Resource:  http://www.icpcanarc.org 