CS 1723, Data Structures, Answers to Final Examination
3. Recursive binary search function:  
  /* from main function */
   index = (int)(M*drand48());
   x = a[index];
   result = bin_search(a, 0, M-1, x);
   printf("Search for: %d, found at %d, same as %d\n",
      x, result, index);
  ...
/* bin_serach: search for x in a from p to r */
int bin_search(int a[], int p, int r, int x)
{
   int q;
   if (p > r) return -1;
   q = (p + r)/2;
   if (a[q] == x) return q;
   if (x < a[q])
      return bin_search(a, p, q-1, x);
   /* else if (x > a[q]) */
   return bin_search(a, q+1, r, x);
}
runner% final_3
Array sorted, 100000 items
Search for: 24311336, found at 24295, same as 24295

4. Command line arguments.
Part(a): All answers Yes.
runnner% cat final_4.c
#include <stdio.h>
void printit(char *argv[]);
void main(int argc, char *argv[])
{
   char *myargv[] = {"mycc", "-o", "prog", "prog.c", NULL};
   char **p = argv;
   printf("Part(b)(i): %s\n", *p);
   printf("Part(b)(i): %c\n", **p);
   printf("Part(b)(i): %s\n", *(p+3));
   printf("Part(b)(i): %c\n", *(*(p+3) + 4));
   printit(argv);
   printit(myargv);
}

void printit(char *argv[])
{
   int line = 0;
   char **p = argv;
   printf("Part(c):Array of Strings:\n");
   while (*p) {  /* or while(*p != NULL) */
      printf("  Line %d:\"%s\"\n", line, *(p++));
      line++;
   }
}
runner% cc -o final_4 final_4.c
runner% final_4 -o prog prog.c  (Extra args not used)
Part(b)(i): final_4
Part(b)(i): f
Part(b)(i): prog.c
Part(b)(i): .
Part(c):Array of Strings:
  Line 0:"final_4"
  Line 1:"-o"
  Line 2:"prog"
  Line 3:"prog.c"
Part(c):Array of Strings:
  Line 0:"mycc"
  Line 1:"-o"
  Line 2:"prog"
  Line 3:"prog.c"

5. Linked list of characters
runner% cat final_5.c
#include <stdio.h>
#include <stdlib.h>

struct lnode {
        char data;
        struct lnode *next;
};

int listlength(struct lnode *list);
struct lnode *makelist(char *s);
void printlist(struct lnode *list);

void main(void)
{
        struct lnode *list;
        char t[] = "Why worry?";
        list = makelist(t);
        printlist(list);
        printf("%d\n", listlength(list));
}

int listlength(struct lnode *list)
{
        int len = 0;
        while (list != NULL) {
                list = list -> next;
                len++;
        }
        return len;
}

void printlist(struct lnode *list)
{
        while (list != NULL) {
                printf("%c", list -> data);
                list = list -> next;
        }
        printf("\n");
}

struct lnode *makelist(char *s)
{
        struct lnode *oldlist = NULL;
        struct lnode *newlist;
        while (*s != '\0') {
                newlist = (struct lnode *)
                          malloc(sizeof(struct lnode));
                newlist -> data = *s;
                newlist -> next = oldlist;
                oldlist = newlist;
                s++;
        }
        return newlist;
}
runner% cc -o final_5 final_5.c
runner% final_5
?yrrow yhW
10