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Last Stone Weight

Detailed guide and Python implementation for the 'Last Stone Weight' problem.

Problem Statement

Easy

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,

- If x != y, the stone of weight x is destroyed, and the stone of weight y has new weight y - x.

At the end of the game, there is at most one stone left.

Return the weight of the last remaining stone. If no stones are left, return 0.

Write a function lastStoneWeight(stones: List[int]) -> int.

Constraints
  • 1 <= len(stones) <= 30
  • 1 <= stones[i] <= 1000

Examples

Example 1
Input
stones = [2,7,4,1,8,1]
Output
1
Explanation

Smash 7 and 8 to get 1, array becomes [2,4,1,1,1]. Smash 2 and 4 to get 2, array becomes [2,1,1,1]. Smash 2 and 1 to get 1, array becomes [1,1,1]. Smash 1 and 1 to get 0, array becomes [1]. The last remaining stone is 1.

Example 2
Input
stones = [1]
Output
1
Explanation

Only one stone, so weight is 1.

Need a Hint?
Consider using Heap / Priority Queue-specific data structures like sets or heaps.
Edge Cases to Watch
  • Empty input structures
  • Single element inputs
  • Large numerical bounds

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