C++ 2D array

Introduction

2D array is an array of arrays. It is used to store multiple data in a table format.
2D array representation

Pseudocode

for i = 0 to 2
  for j = 0 to 3
    arr[i][j] = i + j

C++ code

#include <iostream>
using namespace std;
int main(){

	int arr[3][4] = 
	for(int i = 0; i < 3; i++){
		for(int j = 0; j < 4; j++){
			arr[i][j] = i + j;
		}
	}
}

The above code creates a 3x4 array and assigns the sum of i and j to each element.

0	1	2	3
1	2	3	4
2	3	4	5

Display 2D array

To display a 2D array, you need to use two nested loops to iterate through each element.

You can imagine i is the row and j is the column.

So for each row (i), display value of each "box" (j).

#include <iostream>
using namespace std;
int main(){
	int arr[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
	
	for(int i = 0; i < 3; i++){				// Outer loop for row
		for(int j = 0; j < 3; j++){			// Inner loop for column (each box)
			cout << arr[i][j] << " ";
		}
		cout << endl;					// After finish each row, start a new line
	}
}

Task - Assign consecutive numbers

Fill 1 to 16 in a 4x4 array and output the array.

Final values should be:

1	2	3	4
5	6	7	8
9	10	11	12
13	14	15	16

You need to think about how to fill the array with the correct values by using +-*/ operations to i and j in the loop.

#include <iostream>
using namespace std;
int main(){
	int arr[4][4];
	int i, j;

	for(i = 0; i < 4; i++){
		for(j = 0; j < 4; j++){

		arr[i][j] = _________________________________ ;

		}
	}

	// Display the array with nested loop
  
}

Task - Assign random numbers

Fill a 3x3 array with random numbers between 1 to 9 and output the array.

All numbers should be unique.

Sample output:

4 2 7
5 1 9
3 6 8

Reference

Two Dimensional Array in C++