2091. Removing Minimum and Maximum From Array

Time: O(n)

Space: O(1)

Approach

Find min and max indices; try 3 removal strategies (both from left, both from right, one each side).

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.

Greedy

Greedy algorithms make locally optimal choices at each step, hoping to reach a global optimum. Greedy works when a problem has the "greedy choice property" and "optimal substructure". Common applications: interval scheduling, activity selection, Huffman coding, and jump game.

2091.cs

// Approach: Find min and max indices; try 3 removal strategies (both from left, both from right, one each side).
// Time: O(n) Space: O(1)

public class Solution
{
    public int MinimumDeletions(int[] nums)
    {
        int n = nums.Length;

        int mn = int.MaxValue;
        int mx = int.MinValue;
        int minIndex = -1;
        int maxIndex = -1;

        for (int i = 0; i < n; ++i)
        {
            if (nums[i] < mn)
            {
                mn = nums[i];
                minIndex = i;
            }
            if (nums[i] > mx)
            {
                mx = nums[i];
                maxIndex = i;
            }
        }

        int a = Math.Min(minIndex, maxIndex);
        int b = Math.Max(minIndex, maxIndex);

        // min(delete from front and back,
        //     delete from front,
        //     delete from back)
        return Math.Min(a + 1 + n - b, Math.Min(b + 1, n - a));
    }
}

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