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:

  1. An empty string is stable.
  2. If S is stable, then {S} is also stable.
  3. 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 visa-versa.


Your program will be tested on one or more data sets. Each data set is described on a single line. The line is a non-empty 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.)


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.



Output: 1. 2
2. 0
3. 1

hide comments
insomniac: 2016-02-17 23:09:38

no dp! no stack! O(n) time O(1) space :)

parkjinsang: 2016-02-11 14:47:14

How to solve this problem using dp? anyone?

PRANJIT BHARALI: 2016-02-04 20:11:01

lol.. !!!

try2catch: 2016-01-23 10:35:01

single shot AC problem....... B)
Used stack . Later found that no need of that though.

dwij28: 2016-01-13 06:12:51

150th AC.. Horrible input format.. I got an AC without stack, but my stack solution failed for some unknown reasons.. Also, people who used DP to solve this are trying to cut nails with a sword. DP is so powerful, why waste it on adhoc stuff ?

Akshay Damle: 2015-10-16 18:04:15

Input format weird. Python: WA, C++: AC. Same logic.

Shubham Garg: 2015-09-28 13:03:54

There is definitely some problems in the input when used getchar () for taking input it costed me 4 wrong answers but using scanf got accepted.

topke: 2015-09-24 20:55:30

@arjun well you can do it with just one variable storing information or you can use stack it does not matter since you only store one type of brackets you just need size :D

prakash_reddy: 2015-09-14 20:33:36

easy one stack implementation :) take care of output format costed me 1 WA

simarsher220: 2015-08-30 22:08:13

Last edit: 2015-08-31 17:00:48

Added by:Mohammad Kotb
Time limit:3.236s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ASM64 BASH JS-RHINO