You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly k coins.

Given n, find the total number of full staircase rows that can be formed.

n is a non-negative integer and fits within the range of a 32-bit signed integer.

Example 1:

n = 5

The coins can form the following rows:
¤
¤ ¤
¤ ¤

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

Example 2:

n = 8

The coins can form the following rows:
¤
¤ ¤
¤ ¤ ¤
¤ ¤

Because the 4th row is incomplete, we return 3.

Solutoion

from math import sqrt
class Solution(object):
    def arrangeCoins(self, n):
        """ :type n: int :rtype: int """
        i = int(sqrt(2*n)-1)
        i=0 if(i<0) else i
        while(1):
            if(i*(i+1)<2*n):
                i+=1
            elif(i*(i+1)==2*n):
                break
            else:
                i-=1
                break
        return i

简单题，不解释