following are the strings provided by the user to me -

"1 20";
"1 203";
"1 2030";

in above examples 1 is query and 20,203,2030 are the numbers to be extracted,how can I extract them in C language?

CodePudding user response：

There are many ways to parse a string containing numbers. If you expect the string to have a fixed format with 2 integers, the simplest solution is to use sscanf():

#include <stdio.h>

int parse2numbers(const char *str) {
    int a, b;
    // sscanf returns the number of successful conversions
    int n = sscanf(str, "%d%d", &a, &b);

    if (n == 2) {
        printf("success: a=%d, b=%d\n", a, b);
        return 1;
    }
    if (n == 1) {
        printf("failure: only one number provided: a=%d, str=%s\n", a, str);
        return 0;
    }
    if (n == 0) {
        printf("failure: invalid format: %s\n", str);
        return 1;
    }
    printf("failure: encoding error: n=%d, str=%s\n", n, str);
    return 0;
}

If the string can contain a variable number of integers, you could use strtol() to parse one integer at a time:

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

void parse_numbers(const char *str) {
    long a;
    char *p;
    
    for (;; str = p) {
        errno = 0;
        // strtol returns a long int
        //        updates `p` to point after the number in the source string
        //        sets errno in case of overflow and returns the closest long int
        a = strtol(str, &p, 10);
        if (p == str)
            break;
        if (errno != 0) {
            printf("overflow detected: ");
        }
        printf("got %ld\n", a);
    }
    if (*str) {
        printf("extra characters: |%s|\n", str);
    }
}

CodePudding user response：

I have not tested it but I think theoratically this should work

int rows=2, columns=4 // defining length of array
char ch[rows] [columns] = {"1 90"}, {"2 90"}; // creating two dimentional array for sample data
for (int i = 0; i < rows; i  ) { // looping throw first dimention

// this only works if data is sorted and there is no missing indes in between like [1 200] [3 200] will not work but [1 200] [2 200] should
    char* index;
    if ( ch[i] [0] != itoa(i 1, index, 10) ) // checking if index donot match the row then skip this itteration and move to next one.
        continue; 
    for ( int j = i 2; j<columns; j  ) { // looping through second dimention
        printf("%c\n", ch[i][j]); // printing that second dimention
    }
}