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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 vice-versa.
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 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.)
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
Added by: | Mohammad Kotb |
Date: | 2009-11-28 |
Time limit: | 3.236s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: ASM64 BASH JS-RHINO |
Resource: | http://www.icpc-anarc.org |
hide comments
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2011-12-30 14:27:25 Gaurav
i used stack with O(n) algo and get AC..... |
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2011-12-30 14:27:25 Gabriel
No DP required; this problem can be solved with a simple linear algorithm. A stack or any other data structure isn't necessary either. |
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2011-12-30 14:27:25 Mukhammed Mamasali
who can give an example |
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2011-12-30 14:27:25 rockdude
wat if there are odd no of { ,which can never be made stable by replacing with } or the lik... ? it must be even read input Last edit: 2011-02-05 16:34:01 |
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2011-12-30 14:27:25 Chandra Sekar
yes! Sadly, DP solution gets TLE :( |
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2011-12-30 14:27:25 premanandh_j
i used a stack with O(N) soln but got WA |
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2011-12-30 14:27:25 Kick
Space between 1.<space>answer... Be careful |
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2011-12-30 14:27:25 Nguyen Khac Tung
but if you're able to find a correct & fast greedy algo, it's better :D |
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2011-12-30 14:27:25 Ahmed Kamel [ahm.kam_92]
Yes, i know that's there is a greedy O(N) solution, but dp should get AC like in the contest. |
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2011-12-30 14:27:25 Ambuj Varshney
Think Carefully, a single iteration over each character of the string is sufficient for this question making it in O(N). |