Arranging Coins — LeetCode 441 Python Solution

The problem

You have n coins and you want to build a staircase with these coins. The staircase consists of k rows where the ith row has exactly i coins.

Example

Input

n = 5

Output

2

Explanation

Because the 3rd row is incomplete, we return 2.

Python solution

class Solution:
    def arrangeCoins(self, n: int) -> int:
        return int(math.sqrt(2) * math.sqrt(n + 0.125) - 0.5)

Complexity

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 441. Arranging Coins 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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