2579. Count Total Number of Colored Cells

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Math

Time: O(1)

Space: O(1)

Intuition

Count beautiful arrangements in grid: rows with same count of colored cells and same value modulo k.

Algorithm

1Iterate: count cells colored, track pattern. Combinatorial counting.

Common Pitfalls

•Group by (count mod k). Each group of size g contributes floor(g/2) pairs.

2579.cs

// Approach: After n minutes the colored diamond has n² + (n-1)² cells.
// Time: O(1) Space: O(1)

public class Solution
{
    public long ColoredCells(int n)
    {
        return 1L * n * n + 1L * (n - 1) * (n - 1);
    }
}

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