1014. Best Sightseeing Pair

// Approach: Single pass; track best previous score (value - index); for each position compute score and update the best previous by decrementing.
// Time: O(n) Space: O(1)

public class Solution
{
    public int MaxScoreSightseeingPair(int[] values)
    {
        int ans = 0;
        int bestPrev = 0;

        foreach (var value in values)
        {
            ans = Math.Max(ans, value + bestPrev);
            bestPrev = Math.Max(bestPrev, value) - 1;
        }

        return ans;
    }
}