Problem of The Day: Arranging Coins

Problem Statement

leetcode problem link

Brute Force Approach [Accepted]

class Solution:
    def arrangeCoins(self, n: int) -> int:
        i = 1
        res = 0
        while n >= 0:
            n -= i
            i += 1
            res += 1
        return res - 1

Approach 1: Binary Search

class Solution:
    def arrangeCoins(self, n: int) -> int:
        left, right = 0, n
        while left <= right:
            k = (right + left) // 2
            curr = k * (k + 1) // 2
            if curr == n:
                return k
            if n < curr:
                right = k - 1
            else:
                left = k + 1
        return right