Print repeating diagonal in array

[Dantecross12]

Hi,

I'm trying to print a repeating pattern of numbers, going from 1 to 5, in the diagonal of a 20 x 20 array, but my code isn't producing anything. What am I doing wrong?

#include <iostream>
int main()
{
	int a[20][20];
	int c[5] = { 1,2,3,4,5 };

	for (int i = 0; i < 20; i++)
	{
		for (int j = 0; i < 20; j++)
		{
			if (i != j)
				a[i][j] = 0;
		}
	}

	for (int i = 0; i < 20; i += 5)
	{
		a[i][i] = c[0];
		a[i + 1][i + 1] = c[1];
		a[i + 2][i + 2] = c[2];
		a[i + 3][i + 3] = c[3];
		a[i + 4][i + 4] = c[4];
	}

	for (int i = 0; i < 20; i++)
	{
		for (int j = 0; j < 20; j++)
		{
			std::cout << a[i][j];
		}
		std::cout << '\n';
	}

}

it should be

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

Thank you for your help!

Edit:

NVM, I got it to work using the code below. Is there a better way of doing this though? Thank you

#include <iostream>
int main()
{
	int a[15][15];
	int c[5] = { 1,2,3,4,5 };

	for (int i = 0; i < 15; i++)
	{
		for (int j = 0; j < 15; j++)
		{
			if (i != j);
			a[i][j] = 0;
		}
	}

	for (int i = 0; i < 15; i += 5)
	{
		a[i][i] = c[0];
		a[i + 1][i + 1] = c[1];
		a[i + 2][i + 2] = c[2];
		a[i + 3][i + 3] = c[3];
		a[i + 4][i + 4] = c[4];
	}

	for (int i = 0; i < 15; i++)
	{
		for (int j = 0; j < 15; j++)
		{
			std::cout << a[i][j];
		}
		std::cout << '\n';
	}

}

[Duthomhas]

Use “modular arithmetic”.

The idea is that you have a remainder. For example, the following list of numbers:

    0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
 
can be converted into a repeating range by dividing them by some number (like 5) and keeping the remainder:

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

In C and C++, the “remainder” operator is %, as in:

    remainder = number % divisor;  

The next trick is to see how the index into the array’s diagonal relates to the values you want.

Hope this helps.