Java平衡表达式检查{[（）]} [英] Java balanced expressions check {[()]}

问题描述

我正在尝试创建一个程序，将一个字符串作为参数放入其构造函数中。我需要一个方法来检查字符串是否是一个平衡的括号表达式。它需要处理（{[]}）每个open需要与其相应的右括号进行平衡。例如，用户可以输入[（{}）]，这将是平衡的，而{}将是不平衡的。这不需要处理字母或数字。我需要使用堆栈来执行此操作。

I am trying to create a program that takes a string as an argument into its constructor. I need a method that checks whether the string is a balanced parenthesized expression. It needs to handle ( { [ ] } ) each open needs to balance with its corresponding closing bracket. For example a user could input [({})] which would be balanced and }{ would be unbalanced. This doesn't need to handle letters or numbers. I need to use a stack to do this.

我得到了这个伪代码，但无法确定如何在java中实现它。任何建议都很棒。

I was given this pseudocode but can not figure how to implement it in java. Any advice would be awesome.

更新 - 抱歉忘了发布我到目前为止的内容。这一切搞砸了，因为起初我试图使用char然后我尝试了一个数组..我不确定去哪里。

Update- sorry forgot to post what i had so far. Its all messed up because at first i was trying to use char and then i tried an array.. im not exactly sure where to go.

import java.util.*;

public class Expression
{
  Scanner in = new Scanner(System.in);
  Stack<Integer> stack = new Stack<Integer>();



  public boolean check()
  {
    System.out.println("Please enter your expression.");
    String newExp = in.next();
    String[] exp = new String[newExp];
    for (int i = 0; i < size; i++)
    { 


      char ch = exp.charAt(i);
      if (ch == '(' || ch == '[' || ch == '{')
        stack.push(i);
      else if (ch == ')'|| ch == ']' || ch == '}')
      {
        //nothing to match with
        if(stack.isEmpty())
        {  
          return false;
        }
        else if(stack.pop() != ch)
        { 
          return false;
        } 

      }            
    }
    if (stack.isEmpty())
    {
      return true;
    }
    else
    {
      return false;
    }
  }


}

推荐答案

我希望这段代码可以提供帮助：

I hope this code can help:

import java.util.Stack;

public class BalancedParenthensies {

    public static void main(String args[]) {

        System.out.println(balancedParenthensies("{(a,b)}"));
        System.out.println(balancedParenthensies("{(a},b)"));
        System.out.println(balancedParenthensies("{)(a,b}"));
    }

    public static boolean balancedParenthensies(String s) {
        Stack<Character> stack  = new Stack<Character>();
        for(int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if(c == '[' || c == '(' || c == '{' ) {     
                stack.push(c);
            } else if(c == ']') {
                if(stack.isEmpty() || stack.pop() != '[') {
                    return false;
                }
            } else if(c == ')') {
                if(stack.isEmpty() || stack.pop() != '(') {
                    return false;
                }           
            } else if(c == '}') {
                if(stack.isEmpty() || stack.pop() != '{') {
                    return false;
                }
            }

        }
        return stack.isEmpty();
    }
}

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