84 lines
2.4 KiB
Markdown
84 lines
2.4 KiB
Markdown
---
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title: Identity matrix
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id: 5a23c84252665b21eecc7eb1
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challengeType: 5
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forumTopicId: 302290
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localeTitle: Единичная матрица
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---
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## Description
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<section id='description'>
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<i>Единичная матрица</i> является квадратной матрицей размера \ (n \ times n \), где диагональные элементы - все <b>1</b> s (одни), а все остальные элементы - все <b>0</b> s (нули). \ begin {bmatrix} 1 & 0 & 0 \ cr 0 & 1 & 0 \ cr 0 & 0 & 1 \ cr \ end {bmatrix} Напишите функцию, которая принимает число «n» в качестве параметра и возвращает единичную матрицу порядок nx n.
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</section>
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## Instructions
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<section id='instructions'>
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Write a function that takes a number <code>n</code> as a parameter and returns the identity matrix of order \( n \times n \).
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>idMatrix</code> should be a function.
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testString: assert(typeof idMatrix=='function');
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- text: <code>idMatrix(1)</code> should return an array.
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testString: assert(Array.isArray(idMatrix(1)));
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- text: <code>idMatrix(1)</code> should return <code>[ [ 1 ] ]</code>.
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testString: assert.deepEqual(idMatrix(1),results[0]);
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- text: <code>idMatrix(2)</code> should return <code>[ [ 1, 0 ], [ 0, 1 ] ]</code>.
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testString: assert.deepEqual(idMatrix(2),results[1]);
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- text: <code>idMatrix(3)</code> should return <code>[ [ 1, 0, 0 ], [ 0, 1, 0 ], [ 0, 0, 1 ] ]</code>.
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testString: assert.deepEqual(idMatrix(3),results[2]);
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- text: <code>idMatrix(4)</code> should return <code>[ [ 1, 0, 0, 0 ], [ 0, 1, 0, 0 ], [ 0, 0, 1, 0 ], [ 0, 0, 0, 1 ] ]</code>.
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testString: assert.deepEqual(idMatrix(4),results[3]);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function idMatrix(n) {
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// Good luck!
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}
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```
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</div>
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### After Tests
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<div id='js-teardown'>
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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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</div>
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</section>
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## Solution
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<section id='solution'>
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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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</section>
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