ee1e8abd87
* feat(tools): add seed/solution restore script * chore(curriculum): remove empty sections' markers * chore(curriculum): add seed + solution to Chinese * chore: remove old formatter * fix: update getChallenges parse translated challenges separately, without reference to the source * chore(curriculum): add dashedName to English * chore(curriculum): add dashedName to Chinese * refactor: remove unused challenge property 'name' * fix: relax dashedName requirement * fix: stray tag Remove stray `pre` tag from challenge file. Signed-off-by: nhcarrigan <nhcarrigan@gmail.com> Co-authored-by: nhcarrigan <nhcarrigan@gmail.com>
45 lines
1016 B
Markdown
45 lines
1016 B
Markdown
---
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id: 5900f5091000cf542c51001b
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title: 问题408：通过网格的可允许路径
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challengeType: 5
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videoUrl: ''
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dashedName: problem-408-admissible-paths-through-a-grid
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---
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# --description--
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如果x，y和x + y都是正的正方形，那么我们称格子点（x，y）是不允许的。例如，（9,16）是不允许的，而（0,4），（3,1）和（9,4）则不允许。
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考虑从点（x1，y1）到点（x2，y2）的路径，仅使用北或东的单位步长。如果其中间点都不允许，我们可以称这样的路径是可以接受的。
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令P（n）是从（0,0）到（n，n）的可允许路径的数量。可以证实P（5）= 252，P（16）= 596994440和P（1000）mod 1 000 000 007 = 341920854。
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求P（10 000 000）mod 1 000 000 007。
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# --hints--
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`euler408()`应该返回299742733。
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```js
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assert.strictEqual(euler408(), 299742733);
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```
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# --seed--
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## --seed-contents--
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```js
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function euler408() {
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return true;
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}
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euler408();
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```
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# --solutions--
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```js
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// solution required
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```
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