2018-10-10 22:03:03 +00:00
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---
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id: 5900f4f91000cf542c51000c
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2020-12-16 07:37:30 +00:00
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title: 问题397:抛物线上的三角形
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2018-10-10 22:03:03 +00:00
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challengeType: 5
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videoUrl: ''
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---
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2020-12-16 07:37:30 +00:00
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# --description--
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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在抛物线y = x2 / k上,选择三个点A(a,a2 / k),B(b,b2 / k)和C(c,c2 / k)。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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令F(K,X)为整数四元组(k,a,b,c)的数量,使得三角形ABC的至少一个角度为45度,其中1≤k≤K且-X≤a< b <c≤X。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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例如,F(1,10)= 41并且F(10,100)= 12492.找到F(106,109)。
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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# --hints--
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2018-10-10 22:03:03 +00:00
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2020-12-16 07:37:30 +00:00
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`euler397()`应该返回141630459461893730。
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2018-10-10 22:03:03 +00:00
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```js
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2020-12-16 07:37:30 +00:00
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assert.strictEqual(euler397(), 141630459461893730);
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2018-10-10 22:03:03 +00:00
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```
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2020-12-16 07:37:30 +00:00
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# --solutions--
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2020-08-13 15:24:35 +00:00
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