---
id: 5900f3e61000cf542c50fef9
challengeType: 5
title: 'Problem 122: Efficient exponentiation'
videoUrl: ''
localeTitle: 问题122：有效取幂
---

## Description
<section id="description">最简单的计算n15的方法需要十四次乘法：n×n×...×n = n15但是使用“二进制”方法可以在六次乘法中计算它：n×n = n2n2×n2 = n4n4×n4 = n8n8 ×n4 = n12n12×n2 = n14n14×n = n15然而，只能在五次乘法中计算它：n×n = n2n2×n = n3n3×n3 = n6n6×n6 = n12n12×n3 = n15我们将定义m （k）是计算nk的最小乘法数;例如m（15）= 5.对于1≤k≤200，找到Σm（k）。 </section>

## Instructions
<section id="instructions">
</section>

## Tests
<section id='tests'>

```yml
tests:
  - text: <code>euler122()</code>应返回1582。
    testString: 'assert.strictEqual(euler122(), 1582, "<code>euler122()</code> should return 1582.");'

```

</section>

## Challenge Seed
<section id='challengeSeed'>

<div id='js-seed'>

```js
function euler122() {
  // Good luck!
  return true;
}

euler122();

```

</div>



</section>

## Solution
<section id='solution'>

```js
// solution required
```
</section>
