2018-10-12 15:37:13 -04:00
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---
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title: Learn how a Stack Works
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---
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2019-07-24 00:59:27 -07:00
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# Learn how a Stack Works
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2018-10-12 15:37:13 -04:00
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2019-07-24 00:59:27 -07:00
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---
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## Problem Explanation
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2018-10-12 15:37:13 -04:00
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- Stacks are an abstract data structures.
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- They follow LIFO (Last In First Out) or FILO (First In Last Out) principle.
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- Stack's insertion and deletion operations are of **O(1)** time complexity.
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2019-03-28 09:35:41 +01:00
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- In JavaScript, arrays can be treated as a Stack since `.push()` and `.pop()` methods have time complexity of **O(1)**.
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2018-10-12 15:37:13 -04:00
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- In this challenge we need to `.pop()` and then `.push()` into the stack.
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2019-07-24 00:59:27 -07:00
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---
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## Solutions
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<details><summary>Solution 1 (Click to Show/Hide)</summary>
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2018-10-12 15:37:13 -04:00
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```js
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var homeworkStack = ["BIO12", "HIS80", "MAT122", "PSY44"];
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2018-10-12 15:37:13 -04:00
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homeworkStack.pop();
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homeworkStack.push("CS50");
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```
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2019-07-24 00:59:27 -07:00
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#### Relevant Links
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- [Wikipedia](https://en.wikipedia.org/wiki/Stack_(abstract_data_type))
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- Video by [Hackerrank](https://www.youtube.com/watch?v=wjI1WNcIntg)
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2019-07-24 00:59:27 -07:00
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</details>
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