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3991:Seinfeld

题目描述
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.
输入解释
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.)
输出解释
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.
输入样例
}{
{}{}{}
{{{}
---
输出样例
1. 2
2. 0
3. 1

该题目是Virtual Judge题目,来自 北京大学POJ

题目来源 anarc 2009

源链接: POJ-3991

最后修改于 2020-10-29T07:17:33+00:00 由爬虫自动更新

共提交 0

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