题目
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.
解题思路
台阶的个数是从1到n的，很容易想到1+2+3+...+n = n(n+1)/2,所以比较
i * (i+1)/2 <= n && n < (i+1)(i+2)/2，满足条件的i就是所求的rows
代码
func arrangeCoins(n int) int {
if 0 == n {
return 0
}
var ret int
for i := 0; i <= n; i++ {
if i * (i+1)/2 <= n && n < (i+1)*(i+2)/2 {
ret = i
break
}
}
return ret
}
