LeetCode Problem #441. Arranging Coins

Here is my solution on LeetCode Problem #441. Arranging Coins 

Approach 1: Based on binary search and inequalities

class Solution {
    public int arrangeCoins(int N) {
        long minLevel = 0;
        long maxLevel = N;
        while (minLevel<maxLevel) {
            long midLevel = minLevel + (maxLevel-minLevel+1)/2;
            boolean predicate = ((midLevel*midLevel + midLevel) > (2*(long)N));
            
            if (predicate) {
                maxLevel = midLevel-1;
            }
            else {
                minLevel = midLevel;
            }
        }
        
        if ((minLevel*minLevel + minLevel) > (2*(long)N))
            return -1;
        return (int)minLevel;
    }
}

The time complexity is super-fast: O(lg n) where n is the the input N(the number of coins) and I don't think it can get any faster iteratively.

The only other faster solution I can think of is using SriDharacharya formula to find the roots to inequality:

l^2 + l <= 2*N

where l = last complete level

Do share your thoughts below!

<3
~Take Care