Tour

#include <float.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
  char *name;
  double x, y;
} city_t;
static city_t *new_city(char *name, double x, double y);
static city_t **read_city(FILE *in, int *n);
static double distance(city_t *p1, city_t *p2, city_t *p3);
int main(const int argc, const char **argv);
static city_t *new_city(char *name, double x, double y) {
  city_t *new = (city_t *) malloc(sizeof(city_t));
  new->name = (char *) malloc(strlen(name) + 1);
  strcpy(new->name, name);
  new->x = x;
  new->y = y;
  return new;
}
static city_t **read_city(FILE *in, int *n) {
  city_t ** cities = NULL;
  char name[BUFSIZ];
  double x, y;
  *n = 0;
  while (fscanf(in, "%s%lf%lf", name, &x, &y) != EOF) {
    cities = (city_t **) realloc(cities, ++(*n) * sizeof(city_t *));
    cities[*n - 1] = new_city(name, x, y);
  }
  return cities;
}
static double distance(city_t *p1, city_t *p2, city_t *p3) {
  return sqrt((p1->x - p2->x) * (p1->x - p2->x) + (p1->y - p2->y) * (p1->y - p2->y)) +
      sqrt((p2->x - p3->x) * (p2->x - p3->x) + (p2->y - p3->y) * (p2->y - p3->y)) +
      sqrt((p3->x - p1->x) * (p3->x - p1->x) + (p3->y - p1->y) * (p3->y - p1->y));
}
int main(const int argc, const char **argv) {
  city_t ** cities;
  int n, i, j, k;
  double d, min = DBL_MAX;
  FILE *in = fopen(argv[1], "r");
  cities = read_city(in, &n);
  for (i = 0; i < n; i++)
    for (j = i + 1; j < n; j++)
      for (k = j + 1; k < n; k++) {
        d = distance(cities[i], cities[j], cities[k]);
        printf("%s %s %s: %lf\n", cities[i]->name, cities[j]->name, cities[k]->name, d);
        if (d < min) min = d;
      }
  printf("minimum: %lf\n", min);
  return 0;
}