Binary search solution for 441. Arranging Coins: https://youtu.be/H-Tdu8qJ_uk

ArrangingCoinsBS.java

class ArrangingCoinsBS {
    public int arrangeCoins(int n) {
        int low = 1; 
        int high = n;
        while(low < high) {
            int mid = low +(high -low+1)/2;
            long num = (((long)mid * ((long)mid +1l))/2l);
            if(num == n) {
                return mid;
            } else if(n < num){
                high = mid-1;
            } else {
                low = mid;
            }
        }
        return low;
    }
}