标签：character new match output 实现 private ack close boolean
Given a string containing just the characters ‘(‘, ‘)‘, ‘{‘, ‘}‘, ‘[‘ and ‘]‘, determine if the input string is valid.
给定一个只包含字符‘（‘，‘）‘，‘{‘，‘}‘，‘[‘和‘]‘的字符串，确定输入字符串是否有效。
An input string is valid if:
Note that an empty string is also considered valid.
请注意，空字符串也被视为有效。
Example 1:
Input: "()" Output: true
Example 2:
Input: "()[]{}"
Output: true
Example 3:
Input: "(]" Output: false
Example 4:
Input: "([)]" Output: false
Example 5:
Input: "{[]}"
Output: true
自己写的：
1 class Solution { 2 public boolean isValid(String s) { 3 if(s==null || s.length()==0) return true; 4 Stack<Character> stack=new Stack<>(); 5 for(int i=0;i<s.length();i++){ 6 if(s.charAt(i)==‘(‘ || s.charAt(i)==‘[‘ || s.charAt(i)==‘{‘){ 7 stack.push(s.charAt(i)); 8 }else if(s.charAt(i)==‘)‘ || s.charAt(i)==‘]‘ || s.charAt(i)==‘}‘){ 9 if(stack.isEmpty()){ 10 return false; 11 }else{ 12 char c=stack.peek(); 13 char b=match(c); 14 if(b==s.charAt(i)) 15 stack.pop(); 16 else 17 return false; 18 } 19 } 20 } 21 return stack.isEmpty(); 22 } 23 24 private char match(Character c){ 25 char res; 26 if(c==‘(‘) 27 res=‘)‘; 28 else if(c==‘[‘) 29 res=‘]‘; 30 else 31 res=‘}‘; 32 return res; 33 } 34 }
简洁：
1 class Solution { 2 public boolean isValid(String s) { 3 Stack<Character> stack=new Stack<>(); 4 for(char c:s.toCharArray()){ 5 if(c==‘(‘) 6 stack.push(‘)‘); 7 else if(c==‘[‘) 8 stack.push(‘]‘); 9 else if(c==‘{‘) 10 stack.push(‘}‘); 11 else if(stack.isEmpty() || stack.pop()!=c) 12 return false; 13 } 14 return stack.isEmpty(); 15 } 16 }
典型的用栈实现的问题
标签：character new match output 实现 private ack close boolean
原文地址：https://www.cnblogs.com/chanaichao/p/9613063.html
