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>
100 lines
1.8 KiB
Markdown
100 lines
1.8 KiB
Markdown
---
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id: 5900f36e1000cf542c50fe81
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title: 问题2：斐波那契数列中的偶数
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challengeType: 5
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videoUrl: ''
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dashedName: problem-2-even-fibonacci-numbers
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---
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# --description--
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在斐波那契数列中，每一项都是前两项的和（第一项和第二项除外）。如果从1和2开始，前十项是：
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<div style='text-align: center;'>1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...</div>
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求出斐波那契数列中值是偶数的项的和，至第`n`项（包括第`n`项）为止。
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# --hints--
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`fiboEvenSum(10)`应该返回188。
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```js
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assert.strictEqual(
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fiboEvenSum(10),
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188,
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'<code>fiboEvenSum(10)</code> should return 188.'
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);
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```
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`fiboEvenSum(23)`应该返回60696。
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```js
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assert.strictEqual(
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fiboEvenSum(23),
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60696,
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'<code>fiboEvenSum(23)</code> should return 60696.'
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);
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```
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`fiboEvenSum(43)`应该返回1485607536。
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```js
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assert.strictEqual(
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fiboEvenSum(43),
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1485607536,
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'<code>fiboEvenSum(43)</code> should return 1485607536.'
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);
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```
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您的函数未使用我们的测试值返回正确的结果。
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```js
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assert.strictEqual(
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fiboEvenSum(18),
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3382,
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'Your function is not returning the correct result using our tests values.'
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);
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```
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您的函数应返回`even`数值。
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```js
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assert.equal(
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fiboEvenSum(31) % 2 === 0,
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true,
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'Your function should return an <code>even</code> value.'
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);
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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 fiboEvenSum(n) {
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return true;
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}
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```
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# --solutions--
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```js
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const fiboEvenSum = (number) => {
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if (number <= 1) {
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return 0;
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} else {
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let evenSum = 0,
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prevFibNum = 1,
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fibNum = 2; // According to problem description our Fibonacci series starts with 1, 2
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for (let i = 2; fibNum <= number; i++) {
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if (fibNum % 2 == 0) {
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evenSum += fibNum;
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}
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[prevFibNum, fibNum] = [fibNum, prevFibNum + fibNum];
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}
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return evenSum;
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}
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};
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```
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