C# print stars pattern

Question

I want to print pattern like

but i have a problem with output.

my code is:

int i, j, k;

for (i = 5; i >= 1; i--)
{
    for (j = 5; j > i; j--)
    {
        Console.Write(" ");
    }

    for (k = 1; k < (i * 2); k++)
    {
        Console.Write("*_");
    }

    Console.WriteLine();
}

Console.ReadLine();

Answer 1

There are just a couple of issues:

1. You're writing "*_" for every iteration, including the last. Instead, we should only write "*" on every iteration, followed by "_" on every iteration except the last one. We can do this with two different Console.Write calls, where the second one checks to see if our iterator is at the last position.
2. You're iterating twice as many times as you need to when you do k < (i * 2) (on the first iteration, i == 5, so i * 2 == 10, which means we'll iterate 9 times). We can fix this by changing it to k <= i
3. As a side note, we can declare our loop variables locally in the for loops. This reduces their scope, which is usually a good thing.

For example:

for (int i = 5; i >= 1; i--)
{
    for (int j = 5; j > i; j--)
    {
        Console.Write(" ");
    }

    for (int k = 1; k <= i; k++)
    {
        Console.Write("*");
        if (k < i) Console.Write("_");
    }

    Console.WriteLine();
}

Console.ReadLine();

---

The code can be simplified a little bit if we use the string constructor that takes in a character and a number of times to repeat it to write our spaces, and if we iterate one less time in our inner loop we can write "*_" followed by a WriteLine("*"):

for (int i = 5; i >= 1; i--)
{
    // Write (5 - i) spaces at once
    Console.Write(new string(' ', 5 - i));  

    // Write 'i' count of "*", joined with a "_"
    Console.WriteLine(string.Join("_", Enumerable.Repeat("*", i)));
}

Console.ReadLine();