04 Lesson4 Notes.md

Lesson 4 - Managing Arrays and Strings

Declaring and Initializing Static Arrays

ElementType ArrayName [constant_number of elements] = {optional initial values};

Examples:

int myNumbers [5] = {34, 56, -21, 5002, 365};

int myNumbers [5] = {}; // initializes all integers to 0

int myNumbers [5] = {34, 56};  // initialize first two elements to 34 and 56 and the rest to 0

const int ARRAY_LENGTH = 5;
int myNumbers [ARRAY_LENGTH] = {34, 56, -21, 5002, 365};

int myNumbers [] = {2016, 2052, -525}; // array of 3 elements

Do always initialize arrays, or else they will contain junk values.

How Data Is Stored in an Array

In general, the amount of memory reserved by the compiler for an array in bytes is:
Bytes consumed by an array = sizeof(element-type) * Number of Elements

Accessing and Modifying Data Stored in an Array

int myNumbers [5] = {34, 56, -21, 5002, 365};
// Accessing
cout << myNumbers[0];  // index start from 0 to N-1
// Modifying
myNumbers [3] = 2016;

Fence-Post Error:
It’s named after the fact that the number of posts needed to build a fence is always one more than the number of sections in the fence. You must make sure that the index is not beyond the length of array minus 1.

Multidimensional Arrays

int solarPanels [2][3] = {{0, 1, 2}, {3, 4, 5}};
cout << solarPanels[0][2];  // row 1, column 3 --> 2

Dynamic Arrays - std::vector

#include <iostream>
#include <vector>

using namespace std;

int main(){
  vector<int> dynArray (3);  // dynamic array of int
  
  dynArray[0] = 365;
  dynArray[1] = -421;
  dynArray[2] = 789;
  // ...
}

C-style Character Strings

std::cout << "Hello World"; 

char sayHello[] = {'H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd', '\0'};
std::cout << sayHello << std::endl;

C-style strings are a special case of character arrays in that the last character always precedes the null-terminator '\0'. '\0' is called the string-terminating character.
If you inserted '\0' anywhere in the middle of the array, it would not change the size of the array; it would only mean that string-processing using the array as input would stop at that point.

C++ Strings: Using std::string

#include <iostream> 
#include <string> 

using namespace std;

int main(){
  string greetString ("Hello std::string!");  // Initialization
  cout << greetString << endl;
  cout << greetString.length() << endl;
  \\ ...
}