How to separate words from numbers in file in c

Question

I need to find the degree of inversion for a set of numbers in a file.

I read input from a .txt file in the form:

SET 1: -3 1 2 0 4
SET 2: 0 1 2 3 4 5
SET 4: 29 39 0 1 3

I do not know how to separate the input (the set and its numbers). I thought of putting them in a struct but so far it's not working. The degree of inversion = number of numbers that are smaller than their index value. For example, in SET 2, the degree of inversion is 0.

Answer 1

You need to post code on where you are stuck; that is the best way to get help. Anyway, here is some rough code to help you identify where your issues may be. I have kept it simple to allow you to follow through with how vanilla C does I/O.

#include <stdio.h>                   /* snprinf, fprintf fgets, fopen, sscanf */

int main(void)
{
  char line_buffer[64];
  FILE* infile = fopen("yourfile.txt", "r");         /* open file for reading */
  while(fgets(line_buffer, 64, infile) != NULL)
  {
    char set_name[8];                 /* construct a string w/ the set number */
    snprintf(set_name, 8, "SET %c:", *(line_buffer+4));    /* no. is 5th char */
    fprintf(stdout, "%s ", set_name);           /* fprintf w/ stdout = printf */

    int set[8];
    int ind = 0;
    for(int i=7; line_buffer[i]!='\0';)    /* start from first number and end */
    {                       /* when string ends, denoted by the '\0' sentinel */
      int n;    /* using pointer arithmetric, read in and store num & consume */
      sscanf(line_buffer+i, "%d %n", set+ind, &n);     /* adjacent whitespace */
      i += n;               /* n from sscanf tells how many chars are read in */
      fprintf(stdout, "%d ", set[ind]);
      ind +=1;
    }

    fprintf(stdout, "\n");
  }

  return 0;
}