c# 数学表达式分析（采用逆波兰方式实现）

c# 数学表达式

 

采用逆波兰实现数学表达式求解，如"1+2*9-6" 计算这个字符串的值。

直接贴代码。

使用方法 Caculator c = new Caculator(); double result = c.MathExpressionValue("1+2*6+7-9/2");

 

代码如下：

using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Collections; namespace Caculator { public class Caculator { private string _mathExpression; public Caculator() { } public Caculator( string MathExpression) { _mathExpression = MathExpression; } public string MathExpression { set { _mathExpression = value; } get { return _mathExpression; } } public Double MathExpressionValue() { List<string> ListExp = Parse(this._mathExpression); return Calculate(ListExp); } public Double MathExpressionValue(string MathExpress) { List<string> ListExp = Parse(MathExpress); return Calculate(ListExp); } /// <summary> /// Get Suffix expressions . eg:1+2*3 --> 123*+ /// </summary> /// <param name="MathExpressions"></param> /// <returns></returns> public List<string> Parse(string MathExpressions) { int i, j = 0; string temp,tempSec; Stack myStack = new System.Collections.Stack(); //return value List<string> listResult = new List<string>(); List<string> strListA = StringSpit(MathExpressions); //temp string string[] strB = new string[strListA.Count]; foreach (string strch in strListA) { temp = strch; //if is digit input it to strB[] if (IsOperand(temp)) { strB[j++] = temp; } else { if (temp == "(") myStack.Push(temp); else if (temp == ")") { while (!IsEmpty(myStack)) //Stack pop until ')' { temp = (string)myStack.Pop(); if (temp == "(") break; else strB[j++] = temp; } } else { if (!IsEmpty(myStack)) { do { tempSec = (string)myStack.Pop(); if (Priority(temp) > Priority(tempSec)) { myStack.Push(tempSec); myStack.Push(temp); break; } else { strB[j++] = tempSec; if (IsEmpty(myStack)) { myStack.Push(temp); break; } } } while (!IsEmpty(myStack)); } else { myStack.Push(temp); } } } } while (!IsEmpty(myStack)) strB[j++] = (string)myStack.Pop(); for (i = 0; i < strB.Length; i++) { if(!string.IsNullOrEmpty(strB[i])) { listResult.Add(strB[i]); } } return listResult; } /// <summary> /// Check if is is a digit /// </summary> /// <param name="str"></param> /// <returns>if str is digit, return true else return false</returns> private bool IsOperand(string str) { string[] operators = { "+", "-", "*", "/", "(", ")" }; for (int i = 0; i < operators.Length; i++) if (str == operators[i]) return false; return true; } /// <summary> /// Check Stack empty /// </summary> /// <param name="st"></param> /// <returns></returns> private bool IsEmpty(Stack st) { return st.Count == 0 ? true : false; } /// <summary> /// Spit string with + - * / ( ) /// </summary> /// <param name="StrSource"></param> /// <returns></returns> public List<string> StringSpit(string StrSource) { char[] strarray = StrSource.ToCharArray(); List<string> ListStr = new List<string>(); int start = 0; int LastOpIndex = 0; string temp; for (int i = 0; i < strarray.Length; i++) { switch (strarray[i]) { case '+': case '-': case '*': case '/': case '(': case ')': temp = StrSource.Substring(start, i - start); if (!string.IsNullOrEmpty(temp)) { ListStr.Add(temp); } temp = StrSource.Substring(i, 1); if (!string.IsNullOrEmpty(temp)) { ListStr.Add(temp); } start = i + 1; LastOpIndex = i; break; } if (i == strarray.Length - 1) { ListStr.Add(StrSource.Substring(LastOpIndex + 1, strarray.Length - LastOpIndex - 1)); } } return ListStr; } /// <summary> /// Get operator priority /// </summary> /// <param name="Opr"></param> /// <returns></returns> private int Priority(string Opr) { int priority; switch (Opr) { case "+": priority = 1; break; case "-": priority = 1; break; case "*": priority = 2; break; case "/": priority = 2; break; default: priority = 0; break; } return priority; } /// <summary> /// Calculate suffix express value eg: 123*+ ---> 7 /// </summary> /// <param name="ListstrA"></param> /// <returns></returns> public double Calculate(List<string> ListstrA) { double numFir, numSec, ret; string temp; Stack myStack = new System.Collections.Stack(); foreach (string str in ListstrA) { temp = str; if (IsOperand(temp))//If data, push to stack { myStack.Push(temp); } else //if operate , caculate { object obNum1 = myStack.Pop(); numFir = double.Parse(obNum1.ToString()); object obNum2 = myStack.Pop(); numSec = double.Parse(obNum2.ToString()); ret = GetValue(temp, numFir, numSec); myStack.Push(ret); } } return (double)myStack.Pop(); } /// <summary> /// Get Operate value /// </summary> /// <param name="op"></param> /// <param name="numFir"></param> /// <param name="numSec"></param> /// <returns></returns> private double GetValue(string op, double numFir, double numSec) { switch (op) { case "+": return numSec + numFir; case "-": return numSec - numFir; case "*": return numSec * numFir; case "/": return numSec / numFir; default: return 0; } } } }

 

参考网址：http://www.cnblogs.com/FlyingBread/archive/2007/02/03/638932.html

对算法讲的很清楚。