C#如何从一个字符串读取一个两位数到一个字符

Question

Hi I know this might be a bit silly. But I need to convert my string to a number, and hence I need to use char to loop through the operators. However if I try to do a two or more digit number the number gets broken into single digits. For example.

string str="2+16-42X"

char[] ch=str.toCharArray();

the output comes as(ignore the commas)

2,+,1,6,-,4,2,X

I want to get 2,+,16,-42,X any suggestion on how to work around this? Thank you

Answer 1

You can write a simple lexer:

string str="2+16-42X";

StringBuilder currentNumber = new StringBuilder();
List<string> tokens = new List<string>();

foreach(char chr in str) {
    if (Char.IsDigit(chr)) {
        currentNumber.Append(chr);
    }
    else {
        if (currentNumber.Length > 0) {
            tokens.Add(currentNumber.ToString());
            currentNumber.Clear();
        }
        if (chr == '-') {
            currentNumber.Append(chr);
        }
        else {
            tokens.Add(chr.ToString());
        }
    }
}
if (currentNumber.Length > 0) {
    tokens.Add(currentNumber.ToString());
}

The tokens list contains your numbers and symbols.

Answer 2

Here is a RegEx approach

string str = "2+16-42X";
string[] result = Regex.Matches(str, "-?\\d+|[+/*X]")
                       .Cast<Match>().Select(x => x.Value).ToArray();

explanation:

• -? optional - character at the beginning
• \\d+ one or more digit
• | or
• [+/*X] one of these characters + , / , * , X

https://dotnetfiddle.net/d2ZaGC

Answer 3

You can try to use codes below:

string str = "2+16-42X";

str = str.Replace("+", " +");
str = str.Replace("-", " -");
str = str.Replace("X", " X");

var numbers = str.Split(' ');

foreach (var number in numbers)
{
    Console.WriteLine(number);
}

Output:

2
+16
-42
X

Answer 4

Use RegEx:

string str="2+16-42X";

var match = Regex.Match(str, @"(\d+|\D)+");

match.Groups[1].Captures.Cast<Capture>().Select(c => c.Value).ToList();

returns:

2,+,16,-,42,X