[LeetCode] Arranging Coins
阿新 • • 發佈:2017-10-02
總數 style 方程 stair row bsp nbsp sha arr
You have a total of n coins that you want to form in a staircase shape, where every k-th row must have exactly kcoins.
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.
其實有規律可循,如果將硬幣返回恰好滿足的行數,則硬幣需要1,3,6,10,15...即硬幣的總數滿足x(x+1) = 2n
只要求解這個方程中的x,也就是行數即可。
class Solution { public: int arrangeCoins(int n) { return sqrt(static_cast<double>(n) * 2 + 0.25) - 0.5; } }; // 25 ms
[LeetCode] Arranging Coins