1046

public class Solution {
    public int LastStoneWeight(int[] stones) {
        var pq = new PriorityQueue<int, int>(
            stones.Select(x => (x, x)),
            Comparer<int>.Create((a, b) => b.CompareTo(a)));
 
        while (pq.Count > 1) {
            int x = pq.Dequeue();
            int y = pq.Dequeue();
            if (x > y)
                pq.Enqueue(x - y, x - y);
        }
 
        return pq.Count == 0 ? 0 : pq.Peek();
    }
}

Insert it in a max heap. Keep taking out two stones and do the logic.