C#——编写程序判断给定的表达式字符串中的括号是否正确匹配(成对出现)

例如：

正确的字符串：{[{}{}]}{()},或{{}{}},或者[]{}{}

错误的字符串：{()}[),或{(}),或者({[{

给定字符串：String exp="{()}[{}]";判断是否正确匹配(成对出现)

static void Main(string[] args)
        {
            String exp = "{()}[{}]";
            if (IsCorrect(exp))
            {
                Console.WriteLine("The expression is correct");
            }
            else
            {
                Console.WriteLine("The expression is not correct");
            }
        }

实现方法：

public static bool IsCorrect(string exp)
        {
            int num = 0;//标记
            List<int> numList = new List<int>();
            if (string.IsNullOrEmpty(exp))
            {
                for (int i = 0; i < exp.Length; i++)
                {
                    switch (exp[i])
                    {
                        case '{':
                            num = 3;
                            break;
                        case '[':
                            num = 2;
                            break;
                        case '(':
                            num = 1;
                            break;
                        case '}':
                            num = -3;
                            break;
                        case ']':
                            num = -2;
                            break;
                        case ')':
                            num = -1;
                            break;
                    }
                    if (num > 0)
                        numList.Add(num);
                    if (num < 0)
                    {
                        if (numList[numList.Count - 1] + num == 0)
                            numList.Remove(numList[numList.Count - 1]);
                        else
                            return false;
                    }
                }
            }
            if (numList.Count == 0)
                return true;
            else
                return false;
        }
    }

运行结果：