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75 lines
1.1 KiB
Markdown
75 lines
1.1 KiB
Markdown
---
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id: 598de241872ef8353c58a7a2
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title: 评估二项式系数
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challengeType: 1
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forumTopicId: 302259
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dashedName: evaluate-binomial-coefficients
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---
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# --description--
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Write a function to calculate the binomial coefficient for the given value of n and k.
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写一个函数来计算给定n和k值的二项式系数。
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$\\binom{n}{k} = \\frac{n!}{(n-k)!k!} } = \\ frac {n（n-1）（n-2）\\ ldots（n-k + 1）} { k（k-1）（k-2）\\ ldots 1} $
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# --hints--
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`binom`是一个功能。
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```js
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assert(typeof binom === 'function');
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```
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`binom(5,3)`应该返回10。
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```js
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assert.equal(binom(5, 3), 10);
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```
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`binom(7,2)`应该返回21。
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```js
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assert.equal(binom(7, 2), 21);
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```
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`binom(10,4)`应该返回210。
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```js
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assert.equal(binom(10, 4), 210);
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```
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`binom(6,1)`应该返回6。
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```js
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assert.equal(binom(6, 1), 6);
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```
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`binom(12,8)`应该返回495。
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```js
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assert.equal(binom(12, 8), 495);
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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 binom(n, k) {
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}
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```
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# --solutions--
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```js
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function binom(n, k) {
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let coeff = 1;
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for (let i = n - k + 1; i <= n; i++) coeff *= i;
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for (let i = 1; i <= k; i++) coeff /= i;
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return coeff;
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}
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```
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