44 lines
1.0 KiB
Markdown
44 lines
1.0 KiB
Markdown
---
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title: leetcode-he-wei-sde-lian-xu-zheng-shu-xu-lie-lcof
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date: 2020-04-09 22:14:56
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tags:
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- leetcode
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categories: leetcode
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mathjax: true
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---
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### 面试题57 - II. 和为s的连续正数序列
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[题目](https://leetcode-cn.com/problems/he-wei-sde-lian-xu-zheng-shu-xu-lie-lcof/)
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<!--more-->
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又是小学奥数。由等差数列求和公式$\cfrac{(首项 + 末项)×项数}{2}$ 可知，当首项为 1 的时候项数最多，又由于是连续正整数，$n^2 < (1+n)×n < (n+1)^2 $，那最大的 $n$ 就不大于 $\sqrt{2×target} + 1$。
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由小到大遍历 $n$，可以求得首项。
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```python
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import math
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class Solution:
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def findContinuousSequence(self, target: int):
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n = int(math.sqrt(2 * target) + 1)
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if n < 2:
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return []
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sum_list = []
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a = 0
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for i in range(2, n+1):
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a = ((2 * target) / i + 1 - i) / 2
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if a and not a % 1:
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a = int(a)
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s_ = []
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for j in range(0, i):
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s_.append(a + j)
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sum_list.append(s_)
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return sorted(sum_list)
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# 60 ms 13.7 MB
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```
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