28 lines
726 B
Markdown
28 lines
726 B
Markdown
---
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title: isSorted
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tags: array,intermediate
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---
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Returns `1` if an array of numbers is sorted in ascending order, `-1` if it is sorted in descending order or `0` if it is not sorted.
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- Calculate the ordering `direction` for every pair of adjacent array elements.
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- Return `0` if the `direction` changes or the `direction` sign if the last element is reached.
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```js
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const isSorted = arr => {
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let direction = 0;
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for (let i = 1; i < arr.length; i++) {
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if (!direction) direction = arr[i] - arr[i - 1];
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else 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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