101 lines
2.2 KiB
Markdown
101 lines
2.2 KiB
Markdown
|
---
|
||
|
title: Vector dot product
|
||
|
id: 594810f028c0303b75339ad3
|
||
|
challengeType: 5
|
||
|
forumTopicId: 302343
|
||
|
---
|
||
|
|
||
|
## Description
|
||
|
<section id='description'>
|
||
|
|
||
|
A vector is defined as having three dimensions as being represented by an ordered collection of three numbers: (X, Y, Z).
|
||
|
</section>
|
||
|
|
||
|
## Instructions
|
||
|
<section id='instructions'>
|
||
|
|
||
|
Write a function that takes any numbers of vectors (arrays) as input and computes their dot product. Your function should return <code>null</code> on invalid inputs such as vectors of different lengths.
|
||
|
</section>
|
||
|
|
||
|
## Tests
|
||
|
<section id='tests'>
|
||
|
|
||
|
```yml
|
||
|
tests:
|
||
|
- text: dotProduct should be a function.
|
||
|
testString: assert.equal(typeof dotProduct, 'function');
|
||
|
- text: dotProduct() should return null.
|
||
|
testString: assert.equal(dotProduct(), null);
|
||
|
- text: dotProduct([[1], [1]]) should return 1.
|
||
|
testString: assert.equal(dotProduct([1], [1]), 1);
|
||
|
- text: dotProduct([[1], [1, 2]]) should return null.
|
||
|
testString: assert.equal(dotProduct([1], [1, 2]), null);
|
||
|
- text: dotProduct([1, 3, -5], [4, -2, -1]) should return 3.
|
||
|
testString: assert.equal(dotProduct([1, 3, -5], [4, -2, -1]), 3);
|
||
|
- text: <code>dotProduct(...nVectors)</code> should return 156000.
|
||
|
testString: assert.equal(dotProduct([ 0, 1, 2, 3, 4 ], [ 0, 2, 4, 6, 8 ], [ 0, 3, 6, 9, 12 ], [ 0, 4, 8, 12, 16 ], [ 0, 5, 10, 15, 20 ]), 156000);
|
||
|
|
||
|
```
|
||
|
|
||
|
</section>
|
||
|
|
||
|
## Challenge Seed
|
||
|
<section id='challengeSeed'>
|
||
|
|
||
|
<div id='js-seed'>
|
||
|
|
||
|
```js
|
||
|
function dotProduct(...vectors) {
|
||
|
|
||
|
}
|
||
|
```
|
||
|
|
||
|
</div>
|
||
|
|
||
|
|
||
|
|
||
|
</section>
|
||
|
|
||
|
## Solution
|
||
|
<section id='solution'>
|
||
|
|
||
|
|
||
|
```js
|
||
|
function dotProduct(...vectors) {
|
||
|
if (!vectors || !vectors.length) {
|
||
|
return null;
|
||
|
}
|
||
|
if (!vectors[0] || !vectors[0].length) {
|
||
|
return null;
|
||
|
}
|
||
|
const vectorLen = vectors[0].length;
|
||
|
const numVectors = vectors.length;
|
||
|
|
||
|
// If all vectors not same length, return null
|
||
|
for (let i = 0; i < numVectors; i++) {
|
||
|
if (vectors[i].length !== vectorLen) {
|
||
|
return null; // return undefined
|
||
|
}
|
||
|
}
|
||
|
|
||
|
let prod = 0;
|
||
|
let sum = 0;
|
||
|
let j = vectorLen;
|
||
|
let i = numVectors;
|
||
|
// Sum terms
|
||
|
while (j--) {
|
||
|
i = numVectors;
|
||
|
prod = 1;
|
||
|
|
||
|
while (i--) {
|
||
|
prod *= vectors[i][j];
|
||
|
}
|
||
|
sum += prod;
|
||
|
}
|
||
|
return sum;
|
||
|
}
|
||
|
|
||
|
```
|
||
|
|
||
|
</section>
|