441.Arranging Coins
441.Arranging Coins
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.
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Example 1:
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n = 5
4
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The coins can form the following rows:
6
¤
7
¤ ¤
8
¤ ¤
9
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Because the 3rd row is incomplete, we return 2.
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Example 2:
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n = 8
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The coins can form the following rows:
16
¤
17
¤ ¤
18
¤ ¤ ¤
19
¤ ¤
20
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Because the 4th row is incomplete, we return 3.
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简单的等差数列求项数的题目,一元二次方程求根公式。
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class Solution {
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public:
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int arrangeCoins(int n) {
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return int((sqrt(1+8.0*n)-1)/2);
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}
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};
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执行用时 : 4 ms, 在所有 C++ 提交中击败了96.23%的用户 内存消耗 :8 MB, 在所有 C++ 提交中击败了95.18%的用户
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