Get numbers from string. C

[MisterWhite]

Semifinals on October 24 th - 25 th at Expo, Place de Belgique 1, 1020 Ville de Bruxelles, BelgiumFinals on October 31 at Mercedes-Benz Arena Berlin, Platz 1, 10243 Berlin, Germany

Let's say we have this in text.txt. I can read the file like this:

FILE* stats = fopen ("text.txt", "r");while(!feof(stats) and !ferror(stats)){ fscanf(stats, "%s", &num);printf("%s\t", num);}

"num" will contain each word and number. The task is to extract all numbers from the text. Any ideas?

[LukaP]

you could split it for every word, then check each member of the gained array if its a number. that would be the most intuitive solution. now i assume this is java, so i cant tell you exactly how to do that, or if those numbers when split will automatically become integers or not, but that is just a small language thing to work out)

[MisterWhite]

you could split it for every word, then check each member of the gained array if its a number. that would be the most intuitive solution. now i assume this is java, so i cant tell you exactly how to do that, or if those numbers when split will automatically become integers or not, but that is just a small language thing to work out)

This is in C. Maybe you know how to check in C if it's a number?

[DavidTheWin]

C's string.h has a function called strtok which can split a string into tokens given a set of delimiters. If the input is exactly how you posted it you could split using the delimiters space and comma but you might need to get creative if you need a more general solution. It would be best to have a read of this http://www.cplusplus.com/reference/cstring/strtok/ to see how to use it because it's not very intuitive by modern programming standards.

 

Once you have the string tokenised into the individual words you can check if any of those words are integers using either isnumber (I couldn't find any documentation on this so I'm not sure if it's properly supported) or you could split each word into characters and call isdigit on each of them.

[GER_T4IGA]

This is in C. Maybe you know how to check in C if it's a number?

Well, in ASCII the numbers "0,1,2,3,4,5,6,7,8,9" are coded as "30,31,32,33,34,35,36,37,38,39"(ASCII) if that helps your case in any way.

[Mr_KoKa]

you can write your own function that will loop through every character and check if its one of digit character, if you want to validate signed integers then you need to check if there is '-' character and if it is on the very first position of string.

#include <stdio.h>#include <stdbool.h>#include <string.h>#include <stdlib.h>bool isNumber(const char *s){		size_t l = strlen(s);	if(l == 0) return false;		for(size_t i = 0; i < l; i++){		if((s[i] < '0' || s[i] > '9') && (s[i] != '-' || i > 0)){			return false;		}	}		return true;}int main(){	char text[80];		printf("Enter an integer number: ");	scanf("%s", &text);		if(isNumber(text)){		int number = atoi(text);		printf("%s converted to int = %d\n", text, number);			} else {		printf("%s is not an integer number.\n", text);	}		return 0;	}

And yeah, atoi is function to convert cstring to integer.

[MisterWhite]

you can write your own function that will loop through every character and check if its one of digit character, if you want to validate signed integers then you need to check if there is '-' character and if it is on the very first position of string.

#include <stdio.h>#include <stdbool.h>#include <string.h>#include <stdlib.h>bool isNumber(const char *s){		size_t l = strlen(s);	if(l == 0) return false;		for(size_t i = 0; i < l; i++){		if((s[i] < '0' || s[i] > '9') && (s[i] != '-' || i > 0)){			return false;		}	}		return true;}int main(){	char text[80];		printf("Enter an integer number: ");	scanf("%s", &text);		if(isNumber(text)){		int number = atoi(text);		printf("%s converted to int = %d\n", text, number);			} else {		printf("%s is not an integer number.\n", text);	}		return 0;	}

And yeah, atoi is function to convert cstring to integer.

I'll try it.