有趣的算法 1 有效的括号

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有趣的算法 1 有效的括号

给定一个只包括 ‘(’，’)’，’{’，’}’，’[’，’]’ 的字符串，判断字符串是否有效。

有效字符串需满足：左括号必须用相同类型的右括号闭合。

左括号必须以正确的顺序闭合。

import java.util.Scanner;import java.util.Stack;public class Solution{public boolean isValid(){Scanner input =new Scanner(System.in);String s =input.nextLine();Stack  stack =new Stack<>();char[]  chars =s.toCharArray();if(chars[0]  == '）' || chars[0]  == ']' || chars[0]  == '}'){return false;}for (char aChar :chars) {if(aChar ==' '){continue;}if (stack.empty()) {stack.push(aChar);}else if (isTrue(stack.peek(),aChar)) {stack.pop();}else {stack.push(aChar);}}return stack.empty();}private boolean isTrue(char c1,char c2) {return (c1 =='(' &&c2 ==')') || (c1 =='[' &&c2 ==']') || (c1 =='{' &&c2 =='}');}public static void main(String[]  args) {Solution solution    =  new Solution();System.out.println(solution.isValid());}}