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
ameyanator:
20171221 16:55:11
wrong tag :/ Last edit: 20180125 11:59:49 

vishesh197:
20171215 10:24:19
can be done with dp as well as stack and adhoc as well...But better use stack to understand problem concept..key is to keep track of open braces 

aayush96:
20171004 20:51:05
pathetic problem Last edit: 20171007 10:04:42 

kholan:
20170910 14:14:43
Note that strings such as {}{ are not solvable by only flipping the braces so those problems are not asked. 

mahilewets:
20170828 12:25:04
I have solved it


arora_shivam:
20170824 19:22:51
done in O(n) complexity 

surajmall:
20170809 19:54:33
Need good observation for this problem


jaideeppyne:
20170705 15:03:38
Be careful with the output format. Got 1 WA for that. :( Use adhoc process.No need of stack. You can find a good method of how to approach the question in adhoc way without use of stacks on Quora . The explanation available is nice. 

vivace:
20170630 11:50:42
solvable using dp as well... O(n^2) 

viratian_070:
20170614 07:36:26
no stack needed.....think simple...simple adhoc problem 
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 