看大话数据结构 利用栈实现四则运算这一块儿正好是只有讲解没有代码实现的 于是照着书上的原理自己写了个四则运算的C#代码 以后可以考虑到作为自己的类库中的组件

主要涉及的是逆波兰式 程序主要部分为逆波兰式的产生 以及通过逆波兰式产生最终的四则运算结果

使用的时候只需输入四则运算的算是即可 如2*(1+2)+3*(4+5) 没有中括号大括号 程序会分三个步骤来 首先分割算式 将运算符与数字之间插入空格 方便之后的出入栈操作 如

2 * ( 1 + 2 ) +  3  * ( 4 + 5 )

之后将原式子转变为逆波兰式 最后通过逆波兰式生成最终的算术结果

1.  
   using System;
2.  
   using System.Collections.Generic;
3.  
   using System.Text;
4.  
   using System.Text.RegularExpressions;
5.  
    
6.  
   namespace ConsoleApplication1
7.  
   {
8.  
   class Class1
9.  
   {
10.  
    private static Dictionary<string, int> _operatorLevel;
11.  
     
12.  
    public static void Main(string[] arg)
13.  
    {
14.  
    Console.WriteLine("Type in the source expr");
15.  
    string sourceExpression = Console.ReadLine();
16.  
    Console.WriteLine(InsertBlank(sourceExpression));
17.  
    string rpnExperssion = ConvertToRPN(InsertBlank(sourceExpression));
18.  
    Console.WriteLine(rpnExperssion);
19.  
    Console.WriteLine(GetResult(rpnExperssion));
20.  
    Console.ReadLine();
21.  
    }
22.  
     
23.  
    public static double GetValue(double left, double right, char _operator)
24.  
    {
25.  
    switch (_operator)
26.  
    {
27.  
    case '+':
28.  
    return left+right;
29.  
    case '-':
30.  
    return left-right;
31.  
    case '*':
32.  
    return left*right;
33.  
    case '/':
34.  
    return left/right;
35.  
    }
36.  
    return 0;
37.  
    }
38.  
     
39.  
    public static double GetResult(string source)
40.  
    {
41.  
    Stack<string> stack = new Stack<string>();
42.  
    var list = source.Split(' ');
43.  
    for (int i = 0; i < list.Length; i++)
44.  
    {
45.  
    string current = list[i];
46.  
    if (Regex.IsMatch(current, "^([0-9]{1,}){1}quot;))
47.  
    {
48.  
    stack.Push(current);
49.  
    }
50.  
    else if (OperatorLevel.ContainsKey(current))
51.  
    {
52.  
    double right = double.Parse(stack.Pop());
53.  
    double left = double.Parse(stack.Pop());
54.  
    stack.Push(GetValue(left, right, current[0]).ToString());
55.  
    }
56.  
    }
57.  
    return double.Parse(stack.Pop());
58.  
    }
59.  
     
60.  
    public static string ConvertToRPN(string source)
61.  
    {
62.  
    StringBuilder result = new StringBuilder();
63.  
    Stack<string> stack = new Stack<string>();
64.  
    string[] list = source.Split(' ');
65.  
    for (int i = 0; i < list.Length ; i++)
66.  
    {
67.  
    string current = list[i];
68.  
    if (Regex.IsMatch(current, "^([0-9]{1,}){1}quot;))
69.  
    {
70.  
    result.Append(current + " ");
71.  
    }
72.  
    else if (OperatorLevel.ContainsKey(current))
73.  
    {
74.  
    if (stack.Count > 0)
75.  
    {
76.  
    var prev = stack.Peek();
77.  
    if (prev == "(")
78.  
    {
79.  
    stack.Push(current);
80.  
    continue;
81.  
    }
82.  
    if (current == "(")
83.  
    {
84.  
    stack.Push(current);
85.  
    continue;
86.  
    }
87.  
    if (current == ")")
88.  
    {
89.  
    while (stack.Count > 0 && stack.Peek() != "(")
90.  
    {
91.  
    result.Append(stack.Pop() + " ");
92.  
    }
93.  
    //Pop the "("
94.  
    stack.Pop();
95.  
    continue;
96.  
    }
97.  
    if (OperatorLevel[current] < OperatorLevel[prev])
98.  
    {
99.  
    while (stack.Count > 0)
100.  
     {
101.  
     var top = stack.Pop();
102.  
     if (top != "(" &&
103.  
     top != ")")
104.  
     {
105.  
     result.Append(top + " ");
106.  
     }
107.  
     else
108.  
     {
109.  
     break;
110.  
     }
111.  
     }
112.  
     stack.Push(current);
113.  
     }
114.  
     else
115.  
     {
116.  
     stack.Push(current);
117.  
     }
118.  
     }
119.  
     else
120.  
     {
121.  
     stack.Push(current);
122.  
     }
123.  
     }
124.  
     }
125.  
     if (stack.Count > 0)
126.  
     {
127.  
     while (stack.Count > 0)
128.  
     {
129.  
     var top = stack.Pop();
130.  
     if (top != "(" && top != ")")
131.  
     {
132.  
     result.Append(top + " ");
133.  
     }
134.  
     }
135.  
     }
136.  
     return result.ToString();
137.  
     }
138.  
      
139.  
     public static string InsertBlank(string source)
140.  
     {
141.  
     StringBuilder sb = new StringBuilder();
142.  
     var list = source.ToCharArray();
143.  
     foreach (var temp in list)
144.  
     {
145.  
     if (OperatorLevel.ContainsKey(temp.ToString()))
146.  
     {
147.  
     sb.Append(" ");
148.  
     sb.Append(temp.ToString());
149.  
     sb.Append(" ");
150.  
     }
151.  
     else
152.  
     {
153.  
     sb.Append(temp);
154.  
     }
155.  
     }
156.  
     return sb.ToString();
157.  
     }
158.  
      
159.  
     //运算符字典 方便查询运算符优先级

1.  
   public static Dictionary<string, int> OperatorLevel
2.  
   {
3.  
   get
4.  
   {
5.  
   if(_operatorLevel==null)
6.  
   {
7.  
   _operatorLevel = new Dictionary<string, int>();
8.  
   _operatorLevel.Add("+", 0);
9.  
   _operatorLevel.Add("-", 0);
10.  
    _operatorLevel.Add("(", 1);
11.  
    _operatorLevel.Add("*", 1);
12.  
    _operatorLevel.Add("/", 1);
13.  
    _operatorLevel.Add(")", 0);
14.  
    }
15.  
    return _operatorLevel;
16.  
    }
17.  
    }
18.  
    }
19.