Java: Last Stone Weight

Difficulty Level: EASY

Problem Statement:

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 a new weight y-x.

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

Input:

[2, 7, 4, 1, 8, 1]

Output:

1