检测字符串中的十进制数字和字母 [英] Detect decimal number and alphabet in string

问题描述

我正在编写一个数学应用程序.如何在 c# 中检测字符串中的数字和字母.例如:

I am writing a mathematical application. How can I detect a number and alphabet in string in c#. For Example:

string a = "2x"; // input string
string b = a.Replace("2x","2*x"); // Replace string to add multiplaction sign between a number and variable

可以是整数或双精度数.

It could be an integer or double type number.

推荐答案

regex replace:

regex replace:

var math = new Regex(@"\d[a-zA-Z]");            
var expr = "-2X-4Z-5Y";
string replaced = math.Replace(expr, m => String.Concat(m.Value[0], '*', m.Value[1]));

输出

-2*X-4*Z-5*Y

更新

如果系数和变量之间可以有圆括号，修改replace如下:

if there can be round brackets between coefficient and variable, change replaceas follows:

var math = new Regex(@"\d(\()*[a-zA-Z]");
var expr = "10+2(X+5(a+b))";
string replaced = math.Replace(expr, 
                  m => String.Concat(m.Value[0], "*", m.Value.Substring(1)));

输出

10+2*(X+5*(a+b))

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