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
arjun:
20150730 16:44:45
Hey there is no need to store the stack. Did in O(n). 

aniket_1729:
20150716 15:28:23
output format!!!! 

Ankur Arora:
20150703 01:06:28
very easy 

Alexander007:
20150623 15:22:48
should there be a space between . and answer or not? 

[Mayank Pratap]:
20150622 19:30:50
Stack Implementation....Loved this problem ... :) 

Liquid_Science:
20150618 11:29:30
Got wa because of the space beteween "." and no of operations , well played  _ 

Aman Agarwal:
20150616 14:04:42
take care of the output format..costed me 1 wa..rest is very easy..stack implementation 

Rishabh Joshi:
20150615 06:49:35
Typo in output format cost me 2 wa.. be careful. 

hrishabh:
20150613 22:28:22
easiest one AC in First go :) 

blumonkey:
20150528 19:10:21
What is the significance of '\r' in python. I got AC in cpp but the same algo gave wa in python. Why? 
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 