px[i] <=> (*px + i)

void strcpy(char *dst, char *src)
{
    while(*src != '\0') {
        *dst = *src;
        dst++;
        src++;
    }
}

int main()
{
    char s[] = "hello\n";
    char d[10];

    strcpy(d, s);

    cout << d << endl;

    return 0;
}


void swap(int *x, int *y)
{
    int t = *x;
    *x = *y;
    *y = t;
}

int main()
{
    int x = 1, y = 2;

    swap(&x, &y);
    cout << x << " " << y << endl;
    return 0;
}

* Arrays of pointers

int main()
{
    char *strings[] = {"hello\n", "goodbye\n", "ciao\n"};

    for(i = 0; i < 3; i++) {
        cout << strings[i];
    }
}

* Arguments to your program
#include <iostream>
int main(int argc, char *argv[])
{
    for(int i = 0; i < argc; i++) {
        cout << argv[i] << endl;
    }
}

* Dynamic memory management

#include <iostream>
int main()
{
    int *p = new int;

    *p = 5;

    cout << *p << endl;
}

* Stack vs. Heap

* Dynamically allocated arrays

int main()
{
    int i;
    int n;
    int *nums;

    cout << "How many numbers do you want to sum? ";
    cin > n;

    nums = new int[n];

    for(i = 0; i < n; i++) {
        cout << "Enter number " << i + 1 << ": ";
        cin >> nums[i];
    }

    cout << "The sum is " << sum(nums, n) << endl;

    return 0;
}

* Once you allocate something, it doesn't get deallocated until the program
exits or you deallocate it.

delete x;
delete [] nums;

* Always delete any dynamically allocated memory, or you might run out.

int main()
{
    while(true) {
        int *x = new int;
    }

    return 0;
}

int main()
{
    while(true) {
        int *x = new int;
        delete x;
    }

    return 0;
}

* structures
* create your own data type, combination of other types

struct point {
    double x;
    double y;
};

access individual elements using the '.' operator

struct point p;
p.x = 0.0;
p.y = 0.0;

void translate(struct point& p, int x, int y)
{
    p.x += x;
    p.y += y;
}

struct employee {
    char first[30];
    char last[30];
    char ssn[10];
    double salary;
};

void printEmployee(struct employee emp)
{
    cout << "First name: " << emp.first << endl;
    cout << "Last name: "  << emp.last << endl;
    cout << "SSN: " << emp.ssn << endl;
    cout << "Salary: $" << emp.salary << endl;
}

* pointers to structs

struct employee *emp = new struct employee;
to access a field in the pointer:
(*emp).salary
or
emp->salary

struct employee *createEmp(char *first, char *last, char *ssn, double salary)
{
    struct employee *emp = new struct employee;

    strcpy(emp->first, first);
    strcpy(emp->last, last);
    strcpy(emp->ssn, ssn);
    emp->salary = salary;
 
    return emp;
}

structures can contain pointers to structures of the same type:

struct linkedList {
    struct linkedListNode *head;
    struct linkedListNode *tail;
};

struct linkedListNode {
    int key;
    struct linkedListNode *next;
}

struct linkedList *createLinkedList()
{
    struct linkedList *l = new struct linkedList;

    l->head = NULL;
    l->tail = NULL;
    return l;
}

struct linkedListNode *createLinkedListNode(int key)
{
    struct linkedListNode *n = new struct linkedListNode;

    n->next = NULL;
    n->key = key;

    return n;
}

void insertFront(struct linkedList *list, int key)
{
    struct linkedListNode *n = createLinkedListNode(key);
    
    n->next = list->head;
    list->head = n;

    if(list->tail == NULL) {
        list->tail = n;
    }
}

void insertBack(struct linkedList *list, int key)
{
    struct linkedListNode *n = createLinkedListNode(key);
    
    list->tail = n;

    if(list->tail == NULL) {
        list->head = n;
    } else {
        list->tail->next = n;
    }    
}

void printList(struct linkedList *list)
{
    struct linkedListNode *cur;

    for(cur = list->head; cur != NULL; cur = cur->next) {
        cout << cur->key << " ";
    }
}

void freeList(struct linkedList *list)
{
    struct linkedListNode *cur, *temp;

    for(cur = list->head; cur; cur = temp) {
        temp = cur->next;
        delete cur;
    }
}

int main()
{
    struct linkedList *list = createLinkedList();

    insertFront(list, 1);
    insertFront(list, 2);
    insertFront(list, 3);
    insertFront(list, 4);
    printList(list);
    freeList(list);

    return 0;
}