LeetCode #441 - Arranging Coins

题目描述：

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.

把硬币按照第k行排列k个硬币放置，求在第几行排不满。

class Solution {
public:
    int arrangeCoins(int n) {
        int k=0;
        while(true)
        {
            n-=k;
            if(n<0) break;
            k++;
        }
        return k-1;
    }
};