Last Stone Weight
01 · Problem
You are given an array of integers stones where stones[i] is the weight of the ith stone.
We are playing a game with the stones. On each turn, we choose the heaviest two stones and smash them together. Suppose the heaviest two stones have weights x and y with x <= y. The result of this smash is:
- If
x == y, both stones are destroyed, and - If
x != y, the stone of weightxis destroyed, and the stone of weightyhas new weighty - x.
At the end of the game, there is at most one stone left.
Return the weight of the last remaining stone. If there are no stones left, return 0.
02 · Examples
stones = [2,7,4,1,8,1]
1
Smash 8 and 7 to get 1. Then 4 and 2 to get 2. Then 2 and 1 to get 1. Then 1 and 1 to get 0. Last stone is 1.
stones = [1]
1
There is only one stone, so it is the last remaining stone.
stones = [3,3]
0
Both stones have equal weight. Smashing them destroys both, leaving no stones. Return 0.
03 · Constraints
- 011 <= stones.length <= 30
- 021 <= stones[i] <= 1000
04 · Optimal complexity
- Time
- O(n log n)
- Space
- O(n)
Practice it alone or rehearse it as an interview.
Practice Mode gives you an editor and test runs, nothing else. AI Interview Mode puts a voice interviewer on the other side, adds a clock, and ends with a scored summary of the round.