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  • LeetCode 20. Valid Parentheses

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

    An input string is valid if:

    1. Open brackets must be closed by the same type of brackets.
    2. Open brackets must be closed in the correct order.

    Note that an empty string is also considered valid.

    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
     
    package LeetCode;
    import java.util.HashMap; import java.util.Map; import java.util.Stack; public class L20_ValidParentheses { public boolean isValid(String s) { int len=s.length(); Stack<Character> stack=new Stack<Character>(); if(len==0) return true; if(len%2!=0) return false; Map<Character,Character> map=new HashMap<Character,Character>(); map.put('(',')'); map.put('[',']'); map.put('{','}'); map.put(')',' '); map.put(']',' '); map.put('}',' '); //stack.push(s.charAt(0)); for(int i=0;i<len;i++) { if (stack.empty())//栈为空 stack.push(s.charAt(i)); else if(s.charAt(i)!=map.get(stack.peek()))//或输入与栈顶不匹配 stack.push(s.charAt(i)); else stack.pop(); } if(stack.empty()) return true; else return false; } public static void main(String[] args){ L20_ValidParentheses l20=new L20_ValidParentheses(); String test="([)]"; boolean result=l20.isValid(test); System.out.println(result); } }
    博客园的编辑器没有CSDN的编辑器高大上啊
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  • 原文地址:https://www.cnblogs.com/flowingfog/p/9782171.html
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