441. Arranging Coins

Description: 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 = 5The coins can form the following rows:¤¤ ¤¤ ¤Because the 3rd row is incomplete, we return 2.

Example 2:

n = 8The coins can form the following rows:¤¤ ¤¤ ¤ ¤¤ ¤Because the 4th row is incomplete, we return 3.

解题思路

利用给定的n不停的减去1，2…，直至n小于要减去的数字。

Java-Solution

public class Solution {    public int arrangeCoins(int n) {        if(n < 0)   return -1;        int result = 0;        int add = 1;        while(n >= add){            n -= add;            add++;            result++;        }        return result;    }}