1000. Minimum Cost to Merge Stones
Hard
2.1K
98

There are `n` piles of `stones` arranged in a row. The `ith` pile has `stones[i]` stones.

A move consists of merging exactly `k` consecutive piles into one pile, and the cost of this move is equal to the total number of stones in these `k` piles.

Return the minimum cost to merge all piles of stones into one pile. If it is impossible, return `-1`.

Example 1:

```Input: stones = [3,2,4,1], k = 2
Output: 20
We merge [3, 2] for a cost of 5, and we are left with [5, 4, 1].
We merge [4, 1] for a cost of 5, and we are left with [5, 5].
We merge [5, 5] for a cost of 10, and we are left with .
The total cost was 20, and this is the minimum possible.
```

Example 2:

```Input: stones = [3,2,4,1], k = 3
Output: -1
Explanation: After any merge operation, there are 2 piles left, and we can't merge anymore.  So the task is impossible.
```

Example 3:

```Input: stones = [3,5,1,2,6], k = 3
Output: 25
We merge [5, 1, 2] for a cost of 8, and we are left with [3, 8, 6].
We merge [3, 8, 6] for a cost of 17, and we are left with .
The total cost was 25, and this is the minimum possible.
```

Constraints:

• `n == stones.length`
• `1 <= n <= 30`
• `1 <= stones[i] <= 100`
• `2 <= k <= 30`
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Acceptance Rate
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