C ++ string, character array, and number Conversion

Small things are often very troublesome, that is, they want to use the method of accumulating image indexes to store images. Paste a small piece of code

// Image index No. int ImageIndex = 0; int main (){....... // numeric conversion to string ImageIndex ++; string Index; char index [10]; sprintf_s (index, "% d", ImageIndex); Index = index; string ImageFile = "D: \ test" + Index + ". jpg "; cvSaveImage (& ImageFile [0], & storeImage );.......}

There are two methods to convert a number to a string: one is to use the serial stream under the string; the other is the sprintf and sscanf methods under the C;

Method 1:

Use C ++'s streanstream:

# Include <sstream>
# Include <string>
String num2str (double I)
{
Stringstream ss;
Ss <I;
Return ss. str ();
}

String to numeric:

Int str2num (string s)
{
Int num;
Stringstream ss (s );
Ss> num;
Return num;
}

Method 2:

Sprintf and sscanf in C library are relatively faster

You can use the sprintf function to output the number to a character buffer, and convert the number...
For example:
It is known that the number of seconds (seconds) starting from 0 is calculated as the string "H: M: S", where H is hour, M = minute, S = Second

Int H, M, S;
String time_str;
H = seconds/3600;
M = (seconds % 3600)/60;
S = (seconds % 3600) % 60;
Char ctime [10];
Sprintf (ctime, "% d: % d", H, M, S); // converts an integer to a string
Time_str = ctime; // result

The sscanf function corresponds to sprintf, which can convert strings into numbers.

Char str [] = "15.455 ";
Int I;
Float fp;
Sscanf (str, "% d", & I); // converts a string to an integer I = 15
Sscanf (str, "% f", & fp); // convert the string to a floating point fp = 15.455000
// Print
Printf ("Integer: = % d", I + 1 );
Printf ("Real: = % f", fp + 1 );
Return 0; finally, the first parameter of the cvSaveImage method is of the char * type, and the char * bb = & ImageFile [0] Method for converting a string to a character array;