komxun / cpp-in-21-days-part4

Cpp-in-21-days-Part4

Array

• An array is a sequential collection of data storage locations, each of which holds the same type of sata
• Array element offsets are counted from 0
• SomeArray[n] has n elements that are numbered SomeArray[0] through SomeArray[n-1]

// Inialize an array
int myArray[5];                             // Empty Array of 5 integers
int IntegerArray[5] = {10, 20, 30, 40, 50};
int IntArray[] = {1, 2, 3, 4, 5, 6};        // Compiler automatically picks the array size!

Cpp-in-21-days-Part4/Day 13 - Arrays/const_and_enum_in_Arrays.cpp

Lines 3 to 11 in 659f340

	int main()
	{
	enum WeekDays {Sun, Mon, Tue, Wed, Thu, Fri, Sat, DaysInWeek};
	int ArrayWeek[DaysInWeek] = {10, 20, 30, 40, 50, 60, 70};
	// ArrayWeek is declared to have DaysInWeek elements, which is 7
	std::cout << "The value at Tuesday is: " << ArrayWeek[Tue];
	return 0;
	}

Writing Past the End of an Array

• DON'T write value into an array past the initialized size! The program may crash
• You cannot initialize more elements than you've declared for the array

Arrays of Objects

• When you declare the array to hold objects, you tell the compiler the type of object to store and the number
• The class MUST have a default constructor (takes no arguments) so that the object can be created

Cpp-in-21-days-Part4/Day 13 - Arrays/Arrays_of_Objects.cpp

Lines 5 to 32 in 659f340

	class Cat
	{
	public:
	Cat() {itsAge = 1; itsWeight = 5;} // constructor
	~Cat() {}
	int GetAge() {return itsAge;}
	int GetWeight() {return itsWeight;}
	void SetAge(int age) {itsAge = age;}
	private:
	int itsAge;
	int itsWeight;
	};
	int main()
	{
	Cat Litter[5]; // Array of 5 Cats
	int i;
	for (i=0; i<5; i++)
	{
	Litter[i].SetAge(2*i + 1);
	}
	for (i=0; i<5; i++)
	{
	cout << "Cat #" << i+1 << ": ";
	cout << Litter[i].GetAge() << " years old" << endl;
	}
	return 0;
	}

Multidimensional Arrays (Matrix)

Initializing Multidimensional Arrays

int theArray[5][3] = { {1,2,3},
  {4,5,6},
  {7,8,9},
  {10,11,12},
  {13,14,15}};   // for easy understanding

Array of Pointers

C-style string

• An array of characters that is terminated by a null
• Ex:

char Greeting[] =
{'H','e','l','l','o', ' ', 'W','o','r','l','d','\0'};
// This is equivalent to
char Greeting2[] = "Hello World";

• The last character, \0, is the null character, telling c++ to terminate
• For double-quoted string, the compiler automatically add the null character for you
• Hello World is 12 bytes: Hello=5 bytes, space=1byte, World=5 bytes, and the null character is 1 byte

strcpy() and strncpy()

• strcpy(String2, String1) copies the entire contents of one string into a designated buffer
• strncpy(String2, String1, MaxLength) copies a number of characters from one string to another
• If the source is larger than the destination, strcpy() overwrites past the end of the buffer

Cpp-in-21-days-Part4/Day 13 - Arrays/using_strcpy.cpp

Lines 1 to 16 in 5c19cf1

	// Listing 13.12 - Using strcpy()
	#include <iostream>
	#include <string.h>
	using namespace std;
	int main()
	{
	char String1[] = "No man is an island";
	char String2[80];
	strcpy(String2, String1);
	cout << "String1: " << String1 << endl;
	cout << "String2: " << String2 << endl;
	return 0;
	}

Cpp-in-21-days-Part4/Day 13 - Arrays/using_strncpy.cpp

Lines 1 to 16 in 5c19cf1

	// Listing 13.13 - Using strncpy() (P.436)
	#include <iostream>
	#include <string.h>
	int main()
	{
	const int MaxLength = 80;
	char String1[] = "No man is an island";
	char String2[MaxLength +1];
	strncpy(String2, String1, MaxLength);
	std::cout << "String1: " << String1 << std::endl;
	std::cout << "String2: " << String2 << std::endl;
	return 0;
	}