C＃检查表达式是否为括号有效

表达方式：

“（a [i] + { – 1} *（8-9））”

应该返回true，因为写这样的语法是有效的。 每个左支架在正确的位置都有一个靠近的位置，所有支架都处于合法位置。
我尝试通过一个堆栈来做这个，我知道我错在哪里，但我想知道解决这个问题的相关方法。 谢谢！
我可怜的错误代码：

string expression = "( a[i]+{-1}*(8-9) ) "; Stack expStack = new Stack(); List rightBracketsHolder = new List(); for (int i = 0; i < expression.Length; i++) { if (expression[i] == '{') { expStack.Push('}'); Console.Write("}" + " "); } else if (expression[i] == '(') { expStack.Push(')'); Console.Write(")" + " "); } else if (expression[i] == '[') { expStack.Push(']'); Console.Write("]" + " "); } } Console.WriteLine(); for (int i = 0; i < expression.Length; i++) { if (expression[i] == '}') { rightBracketsHolder.Add('}'); Console.Write(expression[i] + " "); } else if (expression[i] == ')') { rightBracketsHolder.Add(')'); Console.Write(expression[i] + " "); } else if (expression[i] == ']') { rightBracketsHolder.Add(']'); Console.Write(expression[i] + " "); } } Console.WriteLine(); bool stackResult = checkValidity(expStack, rightBracketsHolder); if (stackResult) Console.WriteLine("Expression is Valid."); else Console.WriteLine("\nExpression is not valid."); Console.ReadKey(); } private static bool checkValidity(Stack expStack, List leftBracketsHolder) { Console.WriteLine(); int length = leftBracketsHolder.Count; for (int i = 0; i < length; i++) { if (expStack.Peek().ToString().Contains(leftBracketsHolder.ToString())) { leftBracketsHolder.Remove(expStack.Peek()); expStack.Pop(); } } if (expStack.Count == 0 && leftBracketsHolder.Count ==0) { return true; } return false; } } 

Answer 1

此代码将解决您的目的 –

 static void Main(string[] args) { bool error = false; var str = "( a[i]+{-1}*(8-9) )"; Stack stack = new Stack(); foreach (var item in str.ToCharArray()) { if (item == '(' || item == '{' || item == '[') { stack.Push(item); } else if(item == ')' || item == '}' || item == ']') { if (stack.Peek() != GetComplementBracket(item)) { error = true; break; } } } if (error) Console.WriteLine("Incorrect brackets"); else Console.WriteLine("Brackets are fine"); Console.ReadLine(); } private static char GetComplementBracket(char item) { switch (item) { case ')': return '('; case '}': return '{'; case ']': return '['; default: return ' '; } } 

Answer 2

当关闭发生时，您需要从堆栈中弹出一些东西。 请尝试以下代码。 它将在堆栈上推动一个打开的大括号/括号/括号，然后它将通过相应的关闭从堆栈中弹出。 否则它无效。 如果遇到关闭时堆栈上没有打开，则无效。 如果您在完成后有任何额外的打开，则无效。

我还使用了switch语句而不是if语句，因为我觉得它更容易阅读。

 using System; using System.Collections.Generic; public class Program { public static void Main() { string expression = "( a[i]+{-1}*(8-9) ) "; bool stackResult = checkValidity(expression); if (stackResult) Console.WriteLine("Expression is Valid."); else Console.WriteLine("\nExpression is not valid."); } private static bool checkValidity(string expression) { Stack openStack = new Stack(); foreach (char c in expression) { switch (c) { case '{': case '(': case '[': openStack.Push(c); break; case '}': if (openStack.Count == 0 || openStack.Peek() != '{') { return false; } openStack.Pop(); break; case ')': if (openStack.Count == 0 || openStack.Peek() != '(') { return false; } openStack.Pop(); break; case ']': if (openStack.Count == 0 || openStack.Peek() != '[') { return false; } openStack.Pop(); break; default: break; } } return openStack.Count == 0; } }