3195. Find the Minimum Area to Cover All Ones I

Time: O(mn)

Space: O(1)

Approach

Find bounding box (min/max row and col) of all 1s; return area.

Key Techniques

Array problems involve manipulating elements stored in a contiguous block of memory. Key techniques include two-pointer traversal, prefix sums, sliding windows, and in-place partitioning. In C#, arrays are zero-indexed and fixed in size — use List<T> when you need dynamic resizing.

Matrix

Matrix problems often involve BFS/DFS flood fill, dynamic programming on 2D grids, or spiral/diagonal traversal. For row × column DP, break it into 1D sub-problems column by column. Common pitfalls: boundary checks and modifying the input matrix in-place.

3195.cs

// Approach: Find bounding box (min/max row and col) of all 1s; return area.
// Time: O(mn) Space: O(1)

public class Solution
{
    public int MinimumArea(int[][] grid)
    {
        int x1 = int.MaxValue;
        int y1 = int.MaxValue;
        int x2 = 0;
        int y2 = 0;

        for (int i = 0; i < grid.Length; ++i)
        {
            for (int j = 0; j < grid[0].Length; ++j)
            {
                if (grid[i][j] == 1)
                {
                    x1 = Math.Min(x1, i);
                    y1 = Math.Min(y1, j);
                    x2 = Math.Max(x2, i);
                    y2 = Math.Max(y2, j);
                }
            }
        }

        return (x2 - x1 + 1) * (y2 - y1 + 1);
    }
}

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