EN
C#/.NET - parse number algorithm (atoi)
9 points
xxxxxxxxxx1
public class Parser2
{3
public static int parseInt(string text)4
{5
if (text.Length > 0)6
{7
int value = 0;8
int total = 1;9
10
for (int i = text.Length - 1; i > -1; i -= 1)11
{12
char entry = text[i];13
14
if (entry < '0' || entry > '9')15
throw new FormatException("Incorrect number format.");16
17
value += (entry - '0') * total;18
total *= 10;19
}20
21
return value;22
}23
else24
throw new FormatException("Incorrect number format.");25
}26
}Usage example:
xxxxxxxxxx1
string text = "123";2
int value = Parser.parseInt(text);3
4
Console.WriteLine(value);Output:
xxxxxxxxxx1
123xxxxxxxxxx1
public class Parser2
{3
public static int parseInt(string text)4
{5
if (text.Length > 0)6
{7
int value = 0;8
int total = 1;9
10
Action<char> action = (entry) =>11
{12
if (entry < '0' || entry > '9')13
throw new FormatException("Incorrect number format.");14
15
value += (entry - '0') * total;16
};17
18
for (int i = text.Length - 1; i > 0; i -= 1)19
{20
action.Invoke(text[i]);21
22
total *= 10;23
}24
25
{26
char entry = text[0];27
28
switch (entry)29
{30
case '+':31
return +value;32
33
case '-':34
return -value;35
36
default:37
action.Invoke(entry);38
39
return value;40
}41
}42
}43
else44
throw new FormatException("Incorrect number format.");45
}46
}Usage example:
xxxxxxxxxx1
string text = "123";2
int value = Parser.parseInt(text);3
4
Console.WriteLine(value);Output:
xxxxxxxxxx1
123