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56 lines
1.2 KiB
Markdown
56 lines
1.2 KiB
Markdown
# [921. Minimum Add to Make Parentheses Valid](https://leetcode.com/problems/minimum-add-to-make-parentheses-valid/)
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## 题目
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Given a string S of '(' and ')' parentheses, we add the minimum number of parentheses ( '(' or ')', and in any positions ) so that the resulting parentheses string is valid.
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Formally, a parentheses string is valid if and only if:
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- It is the empty string, or
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- It can be written as AB (A concatenated with B), where A and B are valid strings, or
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- It can be written as (A), where A is a valid string.
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Given a parentheses string, return the minimum number of parentheses we must add to make the resulting string valid.
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Example 1:
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```c
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Input: "())"
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Output: 1
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```
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Example 2:
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```c
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Input: "((("
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Output: 3
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```
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Example 3:
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```c
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Input: "()"
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Output: 0
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```
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Example 4:
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```c
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Input: "()))(("
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Output: 4
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```
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Note:
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1. S.length <= 1000
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2. S only consists of '(' and ')' characters.
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## 题目大意
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给一个括号的字符串，如果能在这个括号字符串中的任意位置添加括号，问能使得这串字符串都能完美匹配的最少添加数是多少。
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## 解题思路
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这题也是栈的题目，利用栈进行括号匹配。最后栈里剩下几个括号，就是最少需要添加的数目。 |