2.5 KiB
2.5 KiB
title | id | challengeType |
---|---|---|
Vector dot product | 594810f028c0303b75339ad3 | 5 |
Description
A vector is defined as having three dimensions as being represented by an ordered collection of three numbers: (X, Y, Z).
Task:
Write a function that takes any numbers of vectors (arrays) as input and computes their dot product.
Your function should return null
on
invalid inputs (ie vectors of different lengths).
Instructions
Tests
tests:
- text: dotProduct must be a function
testString: 'assert.equal(typeof dotProduct, "function", "dotProduct must be a function");'
- text: dotProduct() must return null
testString: 'assert.equal(dotProduct(), null, "dotProduct() must return null");'
- text: 'dotProduct([[1], [1]]) must return 1.'
testString: 'assert.equal(dotProduct([1], [1]), 1, "dotProduct([[1], [1]]) must return 1.");'
- text: 'dotProduct([[1], [1, 2]]) must return null.'
testString: 'assert.equal(dotProduct([1], [1, 2]), null, "dotProduct([[1], [1, 2]]) must return null.");'
- text: 'dotProduct([1, 3, -5], [4, -2, -1]) must return 3.'
testString: 'assert.equal(dotProduct([1, 3, -5], [4, -2, -1]), 3, "dotProduct([1, 3, -5], [4, -2, -1]) must return 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, "<code>dotProduct(...nVectors)</code> should return 156000");'
Challenge Seed
function dotProduct() {
// Good luck!
}
Solution
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;
}