31 lines
849 B
Markdown
31 lines
849 B
Markdown
---
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title: isSorted
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tags: array,intermediate
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firstSeen: 2018-01-01T19:30:14+02:00
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lastUpdated: 2020-10-20T23:02:01+03:00
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---
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Checks if a numeric array is sorted.
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- Calculate the ordering `direction` for the first pair of adjacent array elements.
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- Return `0` if the given array is empty, only has one element or the `direction` changes for any pair of adjacent array elements.
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- Use `Math.sign()` to covert the final value of `direction` to `-1` (descending order) or `1` (ascending order).
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```js
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const isSorted = arr => {
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if (arr.length <= 1) return 0;
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const direction = arr[1] - arr[0];
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for (let i = 2; i < arr.length; i++) {
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if ((arr[i] - arr[i - 1]) * direction < 0) return 0;
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}
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return Math.sign(direction);
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};
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```
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```js
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isSorted([0, 1, 2, 2]); // 1
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isSorted([4, 3, 2]); // -1
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isSorted([4, 3, 5]); // 0
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isSorted([4]); // 0
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```
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