c# 四则运算
2021-07-16 12:13
阅读:697
这是一个计算四则运算的类,个人感觉比较实用,先上代码:
public static class ExpresstionClass { public static string Expresstion;//String类型表达式 ////// 判断字符串是否为数值 /// /// string /// public static bool IsNumberExp(string str) { bool isnumeric = false; byte c; if (str == null || str.Length == 0) return false; System.Text.ASCIIEncoding ascii = new System.Text.ASCIIEncoding(); byte[] bytestr = ascii.GetBytes(str); for (int i = 0; i ) { c = bytestr[i]; if ((c >= 48 && c 57) || c == 46) { isnumeric = true; ; } else { if (c == 45 && bytestr.Length > 1) { isnumeric = true; } else { isnumeric = false; break; } } } return isnumeric; } // 基本一目计算 public static double account(double n1, double n2, string num_op) { double aresult = 0; switch (num_op) { case "+": aresult = n1 + n2; break; case "-": aresult = n1 - n2; break; case "*": aresult = n1 * n2; break; case "/": aresult = n1 / n2; break; } return aresult; } /// /// 将String类型表达式转为由操作数和运算符组成的ArrayList类型表达式 /// /// string /// public static ArrayList Toexp_arraylist(string exp_str) { string exp_element = "", expchar; ArrayList exp_arraylist = new ArrayList(); //遍历表达式 for (int i = 0; i ) { expchar = exp_str.Substring(i, 1); //如果该字符为数字,小数字或者负号(非运算符的减号) if (char.IsNumber(exp_str, i) || expchar == "." || (expchar == "-" && (i == 0 || exp_str.Substring(i - 1, 1) == "("))) { exp_element += expchar;//存为操作数 } else//为运算符 { //将操作数添加到ArrayList类型表达式 if (exp_element != "") exp_arraylist.Add(exp_element); //将运算符添加到ArrayList类型表达式 exp_arraylist.Add(expchar); exp_element = ""; } } //如果还有操作数未添加到ArrayList类型表达式,则执行添加操作 if (exp_element != "") exp_arraylist.Add(exp_element); return exp_arraylist; } //返回运算符的优先级 private static int Operatororder(string op) { switch (op) { case "*": return 3; break; case "/": return 4; break; case "+": return 1; break; case "-": return 2; break; default: return 0; break; } } private static bool IsPop(string op, Stack operators) { if (operators.Count == 0) { return false; } else { if (operators.Peek().ToString() == "(" || Operatororder(op) > Operatororder(operators.Peek().ToString())) { return false; } else { return true; } } } /// /// 将ArrayList类型的中缀表达式转为ArrayList类型的后缀表达式 /// /// ArrayList /// public static ArrayList Toexpback_arraylist(ArrayList exp) { ArrayList expback_arraylist = new ArrayList(); Stack operators = new Stack(); string op; //遍历ArrayList类型的中缀表达式 foreach (string s in exp) { //若为数字则添加到ArrayList类型的后缀表达式 if (IsNumberExp(s)) { expback_arraylist.Add(s); } else { switch (s) { //为运算符 case "+": case "-": case "*": case "/": while (IsPop(s, operators)) { expback_arraylist.Add(operators.Pop().ToString()); } operators.Push(s); break; //为开括号 case "(": operators.Push(s); break; //为闭括号 case ")": while (operators.Count != 0) { op = operators.Pop().ToString(); if (op != "(") { expback_arraylist.Add(op); } else { break; } } break; default: return new ArrayList(); } } } while (operators.Count != 0) { expback_arraylist.Add(operators.Pop().ToString()); } return expback_arraylist; } /// /// 计算一个ArrayList类型的后缀表达式的值 /// /// ArrayList /// public static double ExpValue(ArrayList expback) { double num1, num2, result = 0; Stack num = new Stack(); foreach (string n in expback) { if (IsNumberExp(n)) { num.Push(n); } else { num2 = Convert.ToDouble(num.Pop()); num1 = Convert.ToDouble(num.Pop()); result = account(num1, num2, n); num.Push(result); } } return result; } //返回本类的表达式值 public static double ExpValue() { ArrayList a1 = new ArrayList(); ArrayList a2 = new ArrayList(); a1 = Toexp_arraylist(Expresstion); a2 = Toexpback_arraylist(a1); return ExpValue(a2); } }
使用方法:先调用 Toexp_arraylist方法将String类型表达式转为由操作数和运算符组成的ArrayList类型表达式;然后将返回的ArrayList类型表达式 填入Toexpback_arraylist方法中,返回了一个后缀表达式;最后用ExpValue方法得到处理后的结果
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