Day 12 Recap Questions

  1. What output is printed by the “Example code” below?

     // Example code
 int arr[] = { 94, 69, 35, 72, 9 };
 int *p = arr;
 int *q = p + 3;
 int *r = q - 1;
 printf("%d %d %d\n", *p, *q, *r);
 ptrdiff_t x = q - p;
 ptrdiff_t y = r - p;
 ptrdiff_t z = q - r;
 printf("%d %d %d\n", (int)x, (int)y, (int)z);
 ptrdiff_t m = p - q;
 printf("%d\n", (int)m);
 int c = (p < q);
 int d = (q < p);
 printf("%d %d\n", c, d);

  2. Assume that arr is an array of 5 int elements. Is the code int *p = arr + 5; legal?

  3. Assume that arr is an array of 5 int elements. Is the code int *p = arr + 5; printf("%d\n", *p); legal?

  4. What output is printed by the “Example code 2” below?

     // Example code 2
	
 #include <stdio.h>
	
 int sum(int a[], int n) {
   int x = 0;
   for (int i = 0; i < n; i++) {
     x += a[i];
   }
   return x;
 }
	
 int main(void) {
   int data[] = { 23, 59, 82, 42, 67, 89, 76, 44, 85, 81 };
   int result = sum(data + 3, 4);
   printf("result=%d\n", result);
   return 0;
 }

  5. Suppose we have variables int ra1[10] = {1, 2, 3};, int * ra2 = ra1; and int fun(int *ra); declarations. Will fun(ra1); compile? Will fun(ra2); compile? What if we change the function declaration to int fun(const int ra[]);?

  6. What is the difference, if any, between const int * p and int * const p?

  7. What size of a 2D array does the following define on the heap? Write the code to free memory to prevent memory leakages.

     int **a = malloc(sizeof(int*) * 10);
	
 for (int i = 0; i < 10; i++) {
    a[i] = malloc(sizeof(int) * 5);
 }