难度:Easy
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.
简单的等差数列求项数的题目,一元二次方程求根公式。
class Solution {public:int arrangeCoins(int n) {return int((sqrt(1+8.0*n)-1)/2);}};
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