Click here to download roaches.c.

/*********************************************
This program reads trial data from a roach
experiment, reads a time from the user, and
tells the user where the roach was going at
that point in time.
**********************************************/
#include <stdio.h>
#include <stdlib.h>

/*********************************************
 ** PROTOTYPES & STRUCT DEFINITIONS
 *********************************************/
//--- POINT ---------------------------------//
struct point {
  double x;
  double y;
};
void read_point(struct point* pt, FILE* fin);
void write_point(struct point pt, FILE* fout);

//--- TIME IN HH:MM:SS ----------------------//
struct hhmmss {
  int hrs;
  int mins;
  int secs;
};
void read_hhmmss(struct hhmmss* time, FILE* fin);
int before(struct hhmmss time1, struct hhmmss time2);

//--- A DATA READING FROM THE EXPERIMENT ----//
struct datum {
  struct point position;
  struct hhmmss time;
};
void read_datum(struct datum* dat, FILE* fin);

/*********************************************
 ** MAIN FUNCTION
 *********************************************/
int main() {
  // Open file and read heading info
  int num;
  FILE* fin = fopen("trial.txt", "r");
  fscanf(fin, " %i data listings", &num);

  // Read and store data readings
  struct datum* path = calloc(num, sizeof(struct datum));
  for(int i=0; i < num; ++i) {
    read_datum(&path[i], fin);
  }

  // Get the query time from the user
  struct hhmmss time;
  printf("Enter a time: ");
  fflush(stdout);
  read_hhmmss(&time, stdin);

  // Find the first sighting at or after given time
  int k = 0;
  while (k < num && before(path[k].time, time)) {
    ++k;
  }

  // Write result
  if (k == 0) {
    printf("This was before the first sighting at ");
    write_point(path[0].position, stdout);
  } else if (k == num) {
    printf("This was after the last sighting at ");
    write_point(path[num-1].position, stdout);
  } else {
    printf("The roach was somewhere between ");
    write_point(path[k-1].position, stdout);
    printf(" and ");
    write_point(path[k].position, stdout);
  }
  printf("\n");

  // clean up
  free(path);
  fclose(fin);

  return 0;
}

/*********************************************
 ** FUNCTION DEFINITIONS
 *********************************************/
void read_point(struct point* pt, FILE* fin) {
  fscanf(fin, " ( %lg , %lg )", &pt->x, &pt->y);
}

void write_point(struct point pt, FILE* fout) {
  fprintf(fout, "(%g,%g)", pt.x, pt.y);
}

void read_hhmmss(struct hhmmss* time, FILE* fin) {
  fscanf(fin, "%d:%d:%d", &time->hrs, &time->mins, &time->secs);
}

int before(struct hhmmss time1, struct hhmmss time2) {
  if (time1.hrs != time2.hrs) {
    return time1.hrs < time2.hrs;
  } else if (time1.mins != time2.mins) {
    return time1.mins < time2.mins;
  } else {
    return time1.secs < time2.secs;
  }
}

void read_datum(struct datum* dat, FILE* fin) {
  fscanf(fin, " { [");
  read_hhmmss(&dat->time, fin);
  fscanf(fin, " ] ,");
  read_point(&dat->position, fin);
  fscanf(fin, " }");
}