Make Array Empty — LeetCode 2659 Python Solution

The problem

You are given an integer array nums containing distinct numbers, and you can perform the following operations until the array is empty: If the first element has the smallest value, remove it Otherwise, put the first element at the end of the array. Return an integer denoting the number of operations it takes to make nums empty.

Example

Input

nums = [3,4,-1]

Output

5

Python solution

class Solution:
    def countOperationsToEmptyArray(self, nums: List[int]) -> int:
        pos = {x: i for i, x in enumerate(nums)}
        nums.sort()
        sl = SortedList()
        ans = pos[nums[0]] + 1
        n = len(nums)
        for k, (a, b) in enumerate(pairwise(nums)):
            i, j = pos[a], pos[b]
            d = j - i - sl.bisect(j) + sl.bisect(i)
            ans += d + (n - k) * int(i > j)
            sl.add(i)
        return ans

Complexity

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 2659. Make Array Empty 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.

Related problems