Perfect Square Spiral Pattern in C#
What You’ll Learn
How to generate a perfect square spiral (also called a spiral matrix) in C# using a 2D array.
You’ll fill the grid layer-by-layer using low and high boundaries and print the result with fixed-width formatting.
⭐ Pattern Output
For a 10×10 grid, the pattern looks like this:
1 2 3 4 5 6 7 8 9 10\n36 37 38 39 40 41 42 43 44 11\n35 64 65 66 67 68 69 70 45 12\n34 63 84 85 86 87 88 71 46 13\n33 62 83 96 97 98 89 72 47 14\n32 61 82 95 100 99 90 73 48 15\n31 60 81 94 93 92 91 74 49 16\n30 59 80 79 78 77 76 75 50 17\n29 58 57 56 55 54 53 52 51 18\n28 27 26 25 24 23 22 21 20 19Complete C# Program
Fill a 10×10 array by walking the boundaries in a spiral: top row, right column, bottom row, left column—then move inward.
using System;
namespace MyApp
{
class Program
{
static void Main(string[] args)
{
int[,] arr = new int[10, 10];
int i, j, low = 0, high = 9, n = 1;
for (i = 0; i < 5; i++, low++, high--)
{
for (j = low; j <= high; j++, n++)
arr[i, j] = n;
for (j = low + 1; j <= high; j++, n++)
arr[j, high] = n;
for (j = high - 1; j >= low; j--, n++)
arr[high, j] = n;
for (j = high - 1; j > low; j--, n++)
arr[j, low] = n;
}
Console.WriteLine("Perfect Square Spiral");
for (i = 0; i < 10; i++)
{
Console.WriteLine();
for (j = 0; j < 10; j++)
Console.Write("{0, 4}", arr[i, j]);
Console.WriteLine();
}
}
}
}🧠 How It Works
Create a 2D array
int[,] arr = new int[10,10]; holds the spiral values.
Track the current layer boundaries
low and high mark the current square ring. After each ring, low++ and high--.
Fill 4 sides per layer
Each layer is filled in this order: top row, right column, bottom row, left column, incrementing n each time.
Print with fixed width
Console.Write("{0, 4}", arr[i,j]) keeps columns aligned.
Perfect square spiral
The grid has \(n^2\) cells, so filling and printing takes O(n²) time.
Variation — User Input Size
Generate an \(n \times n\) spiral for any positive n. This version uses four boundaries (top, bottom, left, right) and fills while shrinking them.
using System;
namespace MyApp
{
class Program
{
static void Main(string[] args)
{
Console.Write("Enter size n: ");
if (!int.TryParse(Console.ReadLine(), out int n) || n <= 0)
{
Console.WriteLine("Please enter a positive integer.");
return;
}
int[,] a = new int[n, n];
int top = 0, bottom = n - 1, left = 0, right = n - 1;
int val = 1;
while (top <= bottom && left <= right)
{
for (int j = left; j <= right; j++) a[top, j] = val++;
top++;
for (int i = top; i <= bottom; i++) a[i, right] = val++;
right--;
if (top <= bottom)
{
for (int j = right; j >= left; j--) a[bottom, j] = val++;
bottom--;
}
if (left <= right)
{
for (int i = bottom; i >= top; i--) a[i, left] = val++;
left++;
}
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
Console.Write("{0, 4}", a[i, j]);
Console.WriteLine();
}
}
}
}💡 Tips for Enhancement
Try These
- Use a larger print width if \(n^2\) can exceed 9999
- Reverse the spiral direction by changing the fill order
- Start from the center instead of the border for a different style
- Store the output as a string table for easier alignment control
Avoid
- Printing without fixed width (columns won’t align for 2+ digits)
- Forgetting boundary checks (you may overwrite values or go out of bounds)
- Using an \(n\) so large that the console output becomes unreadable
Key Takeaways
A spiral matrix is generated by filling one border layer at a time.
Boundaries (top/bottom/left/right) make spiral logic easier to manage.
Fixed-width formatting keeps large grids readable.
Time complexity is O(n²) for an \(n \times n\) spiral.
❓ Frequently Asked Questions
Explore More C# Pattern Programs!
Spiral matrices are a great bridge from simple loops to 2D array reasoning.
Spiral-matrix logic shows up in many places: image processing, grid simulations, and interview tasks that require careful boundary control.
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