Arrays in CPP

Pointers

• Definition: A pointer is a variable that holds the memory address of another object (typically another variable).

  • Memory Address Example:
  • 1000 -> 'a'
  • 1004 -> Variable 1 (e.g., var1)
  • 1008 -> Variable 2 (e.g., var2)

• Pointer Variable Declaration:

  • Syntax: <type> *<variable name>
  • Example:
  • int *a; // Pointer to an integer (initial value is garbage)
  • double *b; // Pointer to a double (initial value is garbage)
  • char *c; // Pointer to a char (initial value is garbage)

References

• Definition: A reference is an alternative name (alias) for a variable or an object.
  • Usage: Commonly used in parameter passing to functions.
  • Reference Declaration Syntax:
  • <type> &<variable name> = <variable>
  • Example:
  • int j = 1;
  • int &r = j; // Now r is an alias for j. Changing r changes j.

Address Operator

• Address Operator: & is a unary operator that returns the memory address of a variable.
  • Address Operator Usage:
  • int var1 = 5;
  • int *pint = &var1; // pint points to the address of var1

Arrays

• Relationship with Pointers: An array name is a constant pointer to the first element of the array, meaning we cannot change the address the pointer refers to.
• Array Declaration:
  • Syntax: <type> <array name>[<length>];
  • Example:
  • int a[10];
  • int b[6] = {0, 2, 4, 8, 10, 12}; // Initializes an array with specified values

Array Access

• Accessing Array Elements:
  • Example of Accessing an Element:
  • cout << a[3] << endl; // Outputs 7 if a contains {1, 3, 5, 7, 9}
• Output Address of Array:
  • cout << "The address of a is: " << a << endl;

Traversing Arrays

• Traversing Example:

int a[5];
for (int i=0; i<5; i++) {
    a[i] = i * 2 + 1;
}
for (int i=0; i<5; i++) {
    cout << a[i] << " ";
}

• Output: 1 3 5 7 9

Searching in Arrays

• Search Position in Array:

int search = 7;
for (int i=0; i<5; i++) {
    if (search == a[i]) {
        cout << i << endl;
    }
}

• Example Output: 3

  • Finding Maximum in Array:

int max = a[0];
for (int i=1; i<5; i++) {
    if (max < a[i]) max = a[i];
}
cout << max << endl; // Output: 9

• Finding Minimum in Array:

int min = a[0];
for (int i=1; i<5; i++) {
    if (min > a[i]) min = a[i];
}
cout << min << endl; // Output: 1

Parallel Arrays

• Using Two Parallel Arrays:

int mark[5] = {71, 63, 55, 79, 90};
string name[5] = {"Amy", "Billy", "Cathy", "Debby", "Emily"};
for (int i=0; i<5; i++) {
    cout << name[i] << "'s mark: " << mark[i] << endl;
}

• Example Output:
  • Amy's mark: 71
  • Billy's mark: 63
  • Cathy's mark: 55
  • Debby's mark: 79
  • Emily's mark: 90

2D Arrays

• Declaring a 2D Array:

char board[3][3]={{'O','X','X'},{'O','X','O'},{'X','O','O'}};
for (int i=0; i<3; i++) {
    for (int j=0; j<3; j++) {
        cout << board[i][j] << " ";
    }
    cout << endl;
}

• Example Output:

O X X 
O X O 
X O O