Magnetic Force Between Two Balls — LeetCode 1552 Python Solution

The problem

In the universe Earth C-137, Rick discovered a special form of magnetic force between two balls if they are put in his new invented basket. Rick has n empty baskets, the ith basket is at position[i], Morty has m balls and needs to distribute the balls into the baskets such that the minimum magnetic force between any two balls is maximum.

Example

Input

position = [1,2,3,4,7], m = 3

Output

3

Explanation

Distributing the 3 balls into baskets 1, 4 and 7 will make the magnetic force between ball pairs [3, 3, 6]. The minimum magnetic force is 3. We cannot achieve a larger minimum magnetic force than 3.

Python solution

class Solution:
    def maxDistance(self, position: List[int], m: int) -> int:
        def check(f: int) -> bool:
            prev = -inf
            cnt = 0
            for curr in position:
                if curr - prev >= f:
                    prev = curr
                    cnt += 1
            return cnt < m

        position.sort()
        l, r = 1, position[-1]
        return bisect_left(range(l, r + 1), True, key=check)

Complexity

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 1552. Magnetic Force Between Two Balls is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The monotonic stack guide has the Python template for the pattern and the 225 LeetCode problems that use it.

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