Valid Parentheses leetcode java

题目：

Given a string containing just the characters ‘(‘, ‘)‘, ‘{‘, ‘}‘, ‘[‘ and ‘]‘, determine if the input string is valid.

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

题解：

这道题是一道很常见的老题，记得当时看严蔚敏的数据结构还有数据结构课上面都见过这道题，一道训练栈的基础题。

解题方法是：

一个个检查给的characters，如果是左括号都入栈；如果是右括号，检查栈如果为空，证明不能匹配，如果栈不空，弹出top，与当前扫描的括号检查是否匹配。

全部字符都检查完了以后，判断栈是否为空，空则正确都匹配，不空则证明有没匹配的。

注意：

检查字符是用==，检查String是用.isEqual()，因为String是引用类型，值相等但是地址可能不等。

代码如下：

1     public boolean isValid(String s) {
 2         if(s.length()==0||s.length()==1)
 3             return false;
 4 
 5         Stack<Character> x = new Stack<Character>();
 6         for(int i=0;i<s.length();i++){
 7             if(s.charAt(i)==‘(‘||s.charAt(i)==‘{‘||s.charAt(i)==‘[‘){
 8                 x.push(s.charAt(i));
 9             }else{
10                 if(x.size()==0)
11                     return false;
12                 char top = x.pop();
13                 if(s.charAt(i)==‘)‘)
14                     if(top!=‘(‘)
15                         return false;
16                 else if(s.charAt(i)==‘}‘)
17                     if(top!=‘{‘)
18                         return false;
19                 else if(s.charAt(i)==‘]‘)
20                     if(top!=‘[‘)
21                         return false;
22             }
23     }
24         return x.size()==0;
25 }

Valid Parentheses leetcode java

时间： 2024-10-05 05:06:09

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