89 lines
1.7 KiB
Markdown
89 lines
1.7 KiB
Markdown
---
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id: 5a23c84252665b21eecc7eb1
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title: Identity matrix
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challengeType: 5
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forumTopicId: 302290
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dashedName: identity-matrix
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---
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# --description--
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An *identity matrix* is a square matrix of size \\( n \\times n \\), where the diagonal elements are all `1`s (ones), and all the other elements are all `0`s (zeroes).
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<ul>
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<li style='list-style: none;'>\(\displaystyle I_{n}=\begin{bmatrix} 1 & 0 & 0 \cr 0 & 1 & 0 \cr 0 & 0 & 1 \cr \end{bmatrix}\)</li>
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</ul>
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# --instructions--
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Write a function that takes a number `n` as a parameter and returns the identity matrix of order \\( n \\times n \\).
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# --hints--
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`idMatrix` should be a function.
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```js
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assert(typeof idMatrix == 'function');
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```
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`idMatrix(1)` should return an array.
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```js
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assert(Array.isArray(idMatrix(1)));
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```
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`idMatrix(1)` should return `[ [ 1 ] ]`.
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```js
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assert.deepEqual(idMatrix(1), results[0]);
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```
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`idMatrix(2)` should return `[ [ 1, 0 ], [ 0, 1 ] ]`.
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```js
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assert.deepEqual(idMatrix(2), results[1]);
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```
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`idMatrix(3)` should return `[ [ 1, 0, 0 ], [ 0, 1, 0 ], [ 0, 0, 1 ] ]`.
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```js
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assert.deepEqual(idMatrix(3), results[2]);
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```
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`idMatrix(4)` should return `[ [ 1, 0, 0, 0 ], [ 0, 1, 0, 0 ], [ 0, 0, 1, 0 ], [ 0, 0, 0, 1 ] ]`.
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```js
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assert.deepEqual(idMatrix(4), results[3]);
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```
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# --seed--
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## --after-user-code--
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```js
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let results=[[ [ 1 ] ],
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[ [ 1, 0 ], [ 0, 1 ] ],
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[ [ 1, 0, 0 ], [ 0, 1, 0 ], [ 0, 0, 1 ] ],
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[ [ 1, 0, 0, 0 ], [ 0, 1, 0, 0 ], [ 0, 0, 1, 0 ], [ 0, 0, 0, 1 ] ]]
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```
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## --seed-contents--
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```js
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function idMatrix(n) {
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}
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```
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# --solutions--
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```js
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function idMatrix(n) {
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return Array.apply(null, new Array(n)).map(function (x, i, xs) {
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return xs.map(function (_, k) {
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return i === k ? 1 : 0;
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})
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});
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}
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```
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