> For the complete documentation index, see [llms.txt](https://hao-fu-1.gitbook.io/oj/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hao-fu-1.gitbook.io/oj/heap/1046.-last-stone-weight.md).

# 1046. Last Stone Weight

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

We have a collection of stones, each stone has a positive integer weight.

Each turn, we choose the two **heaviest** stones and smash them together.  Suppose the stones have weights `x` and `y` with `x <= y`.  The result of this smash is:

* If `x == y`, both stones are totally destroyed;
* If `x != y`, the stone of weight `x` is totally destroyed, and the stone of weight `y` has new weight `y-x`.

At the end, there is at most 1 stone left.  Return the weight of this stone (or 0 if there are no stones left.)

**Example 1:**

```
Input: [2,7,4,1,8,1]
Output: 1
Explanation: 
We combine 7 and 8 to get 1 so the array converts to [2,4,1,1,1] then,
we combine 2 and 4 to get 2 so the array converts to [2,1,1,1] then,
we combine 2 and 1 to get 1 so the array converts to [1,1,1] then,
we combine 1 and 1 to get 0 so the array converts to [1] then that's the value of last stone.
```

**Note:**

1. `1 <= stones.length <= 30`
2. `1 <= stones[i] <= 1000`

由正整数构成的数组，每次选值最大的两个元素让它们减去它们中的最小值后把大于0的插回数组，问最后如果剩下一个元素它的值会是多少。动态找最小元素，并能动态更新 => heap。

```cpp
from heapq import heappop, heappush, heapify 
class Solution:
    def lastStoneWeight(self, stones: List[int]) -> int:
        # Creating empty heap 
        heap = [] 
        heapify(heap) 
        # Adding items to the heap using heappush 
        # function by multiplying them with -1 
        for s in stones:
            heappush(heap, -1 * s)
        while len(heap) > 1:
            x, y = -1 * heappop(heap), -1 * heappop(heap)
            if x != y:
                heappush(heap, -1 * abs(y - x))
        return 0 if len(heap) == 0 else -1 * heap[0]

```