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

char *nconcat(const char **str)
{
  int length;        /* For keeping track of the length of the strings. */
  char *rv;          /* The return string. */
  int i;

  /* First, calculate the length of the return string.
     I add one for each string, to account for the spaces between strings,
     and then for the final null character. */

  length = 0;
  for (i = 0; str[i] != NULL; i++) {
    length += strlen(str[i]);
    length++;
  }

  /* Allocate the return string. */

  rv = (char *) malloc(sizeof(char) * length);
  if (rv == NULL) { perror("malloc"); exit(1); }

  /* Build the string incrementally, using the length so that
     strcpy() always starts at the end of rv. */

  strcpy(rv, "");
  length = 0;
  for (i = 0; str[i] != NULL; i++) {
    if (i != 0) {
      strcpy(rv+length, " ");
      length++;
    }
    strcpy(rv+length, str[i]);
    length += strlen(str[i]);
  }

  return rv;
}

int main(int argc, const char **argv)
{
  printf("%s\n", nconcat(argv));
}