Exercise - pointer

[khelkely]

Q1: Trace the partial of program below:

1. int v = 8, *r, *s;
2. int *p;
3. int q = 100;
4. p = &q;
5. r = p;
6. *p = 20;
7. p = new int;
8. *r = 30;
9. q = v;
10. s = p;
11. *s = 50;

What are the last values of *p, q, *r, v and *s?
my answer :
*p = 20
q = ?
*r = 30
v = ?
*s = 50

i can't find q and v. But, if q will point whatever v point, so, the value of q is 8 ? am i right ?



Q2 = Given the following codes:
1. int *p , *q , v , nom[5];
2. p = &v;
3. *p = 12;
4. q = p;
5. nom[0] = *q;
6. p = nom;
7. p++;
8. nom[2] = 12;
9. *p = 13;
10. *q = 10;
11. v = 11;
12. *(p+3) = 16;
13. p = &nom[3];
14. *p = 10;
15. p--;

What are the last values of *p, *q, v and nom ?

my answer :
*p = 10
*q = 10
v = 11
nom = ?

i can't find nom .

Q3 : Given below declaration :

struct Node
{
       int  value;
       Node  * next;
 };

In the main function, the following codes are given:
1. Node *q, *r;
2. Node *p = new Node; //address of this new Node adalah 10000
3. q = r = NULL;
4. p -> value = 9;
5. p -> next = NULL;
6. q = new Node; //address of this new Node adalah 10050
7. p->next = q;
8. p->next->value = 8;
9. q->next = new Node; //address of this new Node adalah 10100
10. r = q;
11. r-> value = 10;
12. q->next->value = 11;
13. q = q-> next;
14. q -> next = NULL;

What are the last values of p->value and q->value ?

my answer :

p->value = 9
q->value = NULL

Anyway, is it relevant my answer?

[Stewbond]

Q1:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

#include <iostream> int main() { int v = 8, *r, *s; // v = 8, r = undefined, s = undefined int *p; // p = undefined int q = 100; // q = 100 p = &q; // p points to q. *p = 100 r = p; // r points to q. *r = 100 *p = 20; // *p = *r = q = 20 p = new int; // p points to something new and undefined, *r = q = 20 still *r = 30; // *r = q = 30 q = v; // *r = q = v = 8 s = p; // s points to the same memory as p, both are undefined *s = 50; // *s = *p = 50 std::cout << "*p = " << *p << std::endl << " q = " << q << std::endl << "*r = " << *r << std::endl << " v = " << v << std::endl << "*s = " << *s << std::endl; }

*p = 50 q = 8 *r = 8 v = 8 *s = 50

[Stewbond]

Q2:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

#include <iostream> int main() { int *p , *q , v , nom[5]; // all undefined p = &v; // *p = v = undefined *p = 12; // *p = v = 12 q = p; // *q = *p = v = 12 nom[0] = *q; // nom[0] gets 12 p = nom; // p = &nom[0], *p = 12 p++; // p = &nom[1] nom[2] = 12; *p = 13; // *p = nom[1] = 13 *q = 10; // *q = v = 10 v = 11; // *q = v = 11 *(p+3) = 16; // p+3 = &nom[1+3]. nom[4] = 16 p = &nom[3]; // *p = undefined *p = 10; // *p = nom[3] = 10 p--; // p = &nom[2]. *p = nom[2] = 12 std::cout << " *p = " << *p << std::endl << " *q = " << *q << std::endl << " v = " << v << std::endl << "nom[0] = " << nom[0] << std::endl << "nom[1] = " << nom[1] << std::endl << "nom[2] = " << nom[2] << std::endl << "nom[3] = " << nom[3] << std::endl << "nom[4] = " << nom[4] << std::endl; }

*p = 12 *q = 11 v = 11 nom[0] = 12 nom[1] = 13 nom[2] = 12 nom[3] = 10 nom[4] = 16

[keskiverto]

12. q->next->value = 11;
13. q = q-> next;

Doesn't q point to a Node, whose value is set?

[Stewbond]

Q3:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

#include <iostream> struct Node { int value; Node* next; }; int main() { // p->next | p->value | q->next | q->value | r->next | r->value Node *q, *r; // - - - - Node *p = new Node; // uninit uninit - - - - q = r = NULL; // uninit uninit - - - - p->value = 9; // uninit 9 - - - - p->next = NULL; // NULL 9 - - - - q = new Node; // NULL 9 uninit uninit - - p->next = q; // q 9 uninit uninit - - p->next->value = 8; // q 9 uninit 8 - - q->next = new Node; // q 9 uninit 8 - - r = q; // q 9 uninit 8 uninit 8 r->value = 10; // q 9 uninit 10 uninit 10 q->next->value = 11;// q 9 uninit 10 uninit 10 q = q->next; // q 9 uninit 11 q 10 q -> next = NULL; // q 9 NULL 11 q 10 std::cout << "p->value: " << p->value << std::endl << "q->value: " << q->value << std::endl << "r->value: " << r->value << std::endl; }

p->value: 9 q->value: 11 r->value: 10