24 lines
760 B
Markdown
24 lines
760 B
Markdown
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---
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title: Learn how a Stack Works
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---
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## Learn how a Stack Works
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### Method:
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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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- In Javascript, arrays can be treated as a Stack since `.push()` and `.pop()` methods have time complexity of **O(1)**.
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- In this challenge we need to `.pop()` and then `.push()` into the stack.
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### Solution:
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```js
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var homeworkStack = ["BIO12","HIS80","MAT122","PSY44"];
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homeworkStack.pop();
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homeworkStack.push("CS50");
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```
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### Reference:
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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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