1046. Last Stone Weight

https://leetcode.com/problems/last-stone-weight/

1. Use priority queue:

//4 ms    7.6 MB
class Solution {
public:
    int lastStoneWeight(vector<int>& A) {
        priority_queue<int> pq (A.begin(), A.end());
        while (pq.size() > 1) {
            int x = pq.top(); 
            pq.pop();
            int y = pq.top(); 
            pq.pop();
            if (x > y) pq.push(x - y);
        }
        return pq.empty() ? 0 : pq.top();
    }
};