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cpp arrays

Arrays

Variables are used to store single piece of data. Arrays can store many piece of data or collection of data. Arrays like variable can store data of a specific datatype. 

#include <iostream>
using namespace std;

int main() {
	int num; //Integer variable
	num = 10; //assignment 
	int num1 = 10; // declare and initialize
	cout << num << endl;
	cout << num1 << endl;

	int nums[3]; //Integer Array
	nums[0] = 2; // assignment
	nums[1] = 5;
	nums[2] = 8;
	int nums1[] = { 4, 2, 4 };
	cout << nums[0] << endl;
	cout << nums[2] << endl;
	cout << nums1[1] << endl;

	return 0;
}



#include <iostream>
using namespace std;

int main() {
	char ch; //declare a char variable
	ch = 'a';

	char chs[5]; //declare an array of 5 char
	chs[0] = 'a';
	chs[1] = 'b';
	chs[2] = 'c';
	chs[3] = 'd';
	chs[4] = 'e';

	cout << "char stored in ch : " << ch << endl;
	cout << "first char stored in chs " << chs[0] << endl;
	cout << "Last char stored in chs " << chs[4] << endl;

 
	return 0;
}
Output: 

#include <iostream>
using namespace std;

int main() {
	char ch; //declare a char variable
	ch = 'a';

	char charArray[5]; //declare an array of 5 char
	charArray[0] = 'a';
	charArray[1] = 'b';
	charArray[2] = 'c';
	charArray[3] = 'd';
	charArray[4] = 'e';

	char chs2[] = {'f', 'g', 'h', 'i'};
	char chs3[] = "myword";

	cout << "char stored in ch : " << ch << endl;
	cout << "first char stored in chs " << charArray[0] << endl;
	cout << "Last char stored in chs " << charArray[4] << endl;
	cout << "first char stored in chs2 " << chs2[0] << endl;
	cout << "Last char stored in chs2 " << chs2[3] << endl;
	cout << "first char stored in chs3 " << chs3[0] << endl;
	cout << "first char stored in chs3 " << chs3[5] << endl;
	cout << "Last char stored in chs3 " << chs3[6] << endl;
	return 0;
}
Output: 

#include <iostream>
#include <string>
using namespace std;

int main() {
	string items[10];
	for (int i = 0; i < 3; i++)
	{
		cout << "Enter the item : ";
		cin >> items[i];
	}
	for (string item: items)
	{
		cout << item << "\t";
	}
	cout << endl;
	for (int i = 0; i < 5; i++)
	{
		cout << i+1 << ") " << items[i] << "\n";
	}
	return 0;
}
Output:

Traversing an array with for each loop


#include 
#include 
using namespace std;

int main() {
	string month[] = { "Jan", "Feb", "Mar", "Apr",
						"May", "Jun", "Jul", "Aug",
						"Sep", "Oct", "Nov", "Dec" };

	cout << month[3] << endl << endl; //This prints 4th element

	//using for each loop to traverse through the array
	for (string var : month)
	{
		cout << var << endl;
	}

	return 0;
}

Parallel Arrays



#include 
#include 
using namespace std;

int main() {
	const int NUM_EL = 3;

	string items[NUM_EL];
	double prices[NUM_EL];
	for (int i = 0; i < NUM_EL; i++){
		cout << "Enter the item : ";
		cin >> items[i];
		cout << "\t Enter the price : ";
		cin >> prices[i];
	}
	for (int i = 0; i < NUM_EL; i++){
		cout << i+1 << ") " << items[i] << "\t" << prices[i] << "\n";
	}
	return 0;
}



#include 
using namespace std;

int main() {
	//Parallel Arrays - Array with two different datatypes
	string month[] = { "Jan", "Feb", "Mar", "Apr",
						"May", "Jun", "Jul", "Aug",
						"Sep", "Oct", "Nov", "Dec" };
	int monthdays[] = { 31,28,31,30,
						31,30,31,31,
						30,31,30,31 };

	cout << "month[i]" << "\t" << "monthdays[i]" << endl;
	for (int i = 0;  i < 12;  i++)
	{
		cout << month[i] << "\t\t" << monthdays[i] << endl;
	}

	return 0;
}
Here is another example. This time we will populate the array by accepting the inputs from the user. 


#include 
#include 
using namespace std;
int main() {
	//Parallel Arrays - Array with two different datatypes
	string month[12];
	int monthdays[12];
	for (int i = 0; i < 12; i++)
	{
		cout << "Month: ";
		cin >> month[i];
		cout << "\t Days in this month: ";
		cin >> monthdays[i];
	}

	cout << "month[i]" << "\t" << "monthdays[i]" << endl;
	for (int i = 0;  i < 12;  i++)
	{
		cout << month[i] << "\t\t\t" << monthdays[i] << endl;
	}
	return 0;
}

Multi Dimensional Array

2D Array


#include <iostream>
#include <string>
using namespace std;
int main() {
	//2D Array - 12 rows and 2 columns
	string month[12][2] = { 
    	{"Jan", "January"},
		{"Feb", "February"},
		{"Mar", "March"},
		{"Apr", "April"},
		{"May", "May"},
		{"Jun", "June"},
		{"Jul", "July"},
		{"Aug", "August"},
		{"Sep", "September"},
		{"Oct", "October"},
		{"Nov", "November"},
		{"Dec", "December"} };
	int monthdays[] = { 31,28,31,30,
						31,30,31,31,
						30,31,30,31 };

	//cout << "month[i]" << "\t" << "monthdays[i]" << endl;
	for (int i = 0;  i < 12;  i++)
	{
		cout << month[i][0] << "\t" << month[i][1] 
			<< "\t\t" << monthdays[i] << endl;
	}
	return 0;
}
output:

Passing array to the function

In the following program, the array is passed to a function. 


#include <iostream>
#include <string>
using namespace std;

void printArray(string arr[12][2], int arr2[12])
{
	for (int i = 0; i < 12; i++)
	{
		cout << arr[i][0] << "\t" << arr[i][1]
			<< "\t\t" << arr2[i] << endl;
	}
	return;
}

void changeDays(string arr[12][2], int arr2[12])
{
	int mon,days;
	cout << "Enter the month to change the days for (1-12):";
	cin >> mon;
	cout << "Enter the number of days :";
	cin >> days;
	arr2[mon - 1] = days;
	return;
}

int main() {
	//2D Array - 12 rows and 2 columns
	string month[12][2] = { 
    	{"Jan", "January"},						
    	{"Feb", "February"},
		{"Mar", "March"},
		{"Apr", "April"},
		{"May", "May"},
		{"Jun", "June"},
		{"Jul", "July"},
		{"Aug", "August"},
		{"Sep", "September"},
		{"Oct", "October"},
		{"Nov", "November"},
		{"Dec", "December"} };
	int monthdays[] = { 31,28,31,30,
						31,30,31,31,
						30,31,30,31 };

	do
	{
		int opt;
		cout << "Main menu" << endl;
		cout << "=========" << endl;
		cout << "1. Change days of a month." << endl;
		cout << "2. Print the month and days." << endl;
		cout << "3. Exit." << endl;
		cout << "Enter your selection: ";
		cin >> opt;

		switch (opt)
		{
		case 1:
			changeDays(month, monthdays);
			break;
		case 2:
			printArray(month, monthdays);
			break;
		case 3:
			cout << "Exiting program";
			exit(0);
			break;
		default:
			cout << "Invalid Option"; 
			break;
		}
	} while (true);
}
output: 


#include <iostream>
#include <string>
using namespace std;
void GetInfo(string arrItem[3], double arrPrice[3]);
void PrintInfo(string arrItem[3], double arrPrice[3]);
int main() {
	string items[3];
	double prices[3];
	do {
		int opt;
		cout << "Menu" << endl;
		cout << "1. Get Info" << endl;
		cout << "2. Print Info" << endl;
		cout << "3. Exit" << endl;
		cout << "What do you want to do? : ";
		cin >> opt;
		switch (opt)
		{
		case 1:
			GetInfo(items, prices);
			break;
		case 2: 
			PrintInfo(items, prices);
			break;
		case 3:
			cout << "Thank you for using this program." ;
			exit(0);
			break;
		default:
			cout << "Invalid option. Enter 1-3.";
			break;
		}
	} while (true);
	return 0;
}
void GetInfo(string arrItem[3], double arrPrice[3]) {
	for (int i = 0; i < 3; i++) {
		cout << "Enter the item : ";
		cin >> arrItem[i];
		cout << "\t Enter the price : ";
		cin >> arrPrice[i];
	}
}
void PrintInfo(string arrItem[3], double arrPrice[3]) {
	for (int i = 0; i < 3; i++) {
		cout << i + 1 << ") " << arrItem[i] << "\t" << arrPrice[i] << "\n";
	}
}
Output:

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