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

//
// Purpose:	Demonstrate parts of the C/C++ assessment.
// 
//

int   n[10] = { 5, 3, 7, 6, 15, 8, 10};

int
foo1 (int a) {
  int       b, c;
  c = 0;
  while (a) {
    b = a%10;
    c = c*10 + b;
    a = a/10;
  }
  return c;
}

int
foo2 ( int n[], int nitems) {
  int     j, k;

  j = n[nitems-1];
  for (k = nitems-2; k >= 0; k-- ) {
    if (j > n[k])       j = n[k];
  }
  return j;
}

main ( ) {
  printf("Problem 2:  c = %d\n\n", foo1(567));

  printf("Problem 3:  foo2 = %d\n\n", foo2(n,7));

  {	// Problem 4
    int   x = 10;
    int   y = 20;
    int   z;
    int   *px = &x;
    int   *py = &y;

    z = (*px)++;
    printf("Problem 4a (z, x):  %d, %d\n", z, x);
    z = (*py) + y;
    printf("Problem 4b (z, y):  %d, %d\n", z, y);
    printf("Problem 4c:  Invalid since x and y are not pointers\n\n");
  }

  {	// Problem  5
    char   s[] = "abcd";
    char   *p = s;

    printf("Problem 5\n");
    p++;
    printf("%s ", p);
    (*p)++;
    printf("%s ", s);
    printf("\n\n");
  }

  {	// Problem 6
    // char  *A[] = { "I", "am", "in", "CSE 422S" }; won't work
    // because the strings are in read-only memory.  The following
    // duplicates each string before assigning it to a char pointer.
    char  *A[] = { strdup("I"), strdup("am"), strdup("in"),
    						strdup("CSE 422S") };
    printf("Problem 6a (before):  <");
    for (int i=0; i<4; i++)	printf("%s ", A[i]);
    printf(">\n");
    for (int i=0; i<4; i++)	printf("%x ", A[i]);
    printf("\n\n");

    strcpy(A[3], "422S");
    printf("Problem 6a (after):  <");
    for (int i=0; i<4; i++)	printf("%s ", A[i]);
    printf(">\n\n");

    strcpy(A[3], "CSE 422S");	// restore value

    printf("Problem 6b (before):  <");
    for (int i=0; i<4; i++)	printf("%s ", A[i]);
    printf(">\n\n");

    char	*B = "422S";
    strncpy(A[3], B, strlen(B));
    printf("Problem 6b (after):  <");
    for (int i=0; i<4; i++)	printf("%s ", A[i]);
    printf(">\n\n");
  }

  {	// Problem 6 alternative
    // char  *A[] = { "I", "am", "in", "CSE 422S" }; won't work
    // because the strings are in read-only memory.  The following
    // will allocate space for the 4 by 9 array and then initialize
    // it with the characters that make up the strings.
    char  A[][9] = { "I", "am", "in", "CSE 422S" };
    char  *p[] = { &(A[0][0]), &(A[1][0]), &(A[2][0]), &(A[3][0]) };

    printf("Problem 6a (before):  <");
    for (int i=0; i<4; i++)	printf("%s ", p[i]);
    printf(">\n");
    for (int i=0; i<4; i++)	printf("%x ", p[i]);
    printf("\n\n");

    strcpy(p[3], "422S");
    printf("Problem 6a (after):  <");
    for (int i=0; i<4; i++)	printf("%s ", p[i]);
    printf(">\n\n");

    strcpy(p[3], "CSE 422S");	// restore value

    printf("Problem 6b (before):  <");
    for (int i=0; i<4; i++)	printf("%s ", p[i]);
    printf(">\n\n");

    char	*B = "422S";
    strncpy(p[3], B, strlen(B));
    printf("Problem 6b (after):  <");
    for (int i=0; i<4; i++)	printf("%s ", p[i]);
    printf(">\n\n");
  }

}