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30 lines
1.2 KiB
30 lines
1.2 KiB
---
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id: math
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title: Math
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---
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## Notes
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If code involves division or modulo, remember to check for division or modulo by 0 case.
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When a question involves "a multiple of a number", perhaps modulo might be useful.
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Check for and handle overflow/underflow if you are using a typed language like Java and C++. At the very least, mention that overflow/underflow is possible and ask whether you need to handle it.
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Consider negative numbers and floating point numbers. This may sound obvious, but under interview pressure, many obvious cases go unnoticed.
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If the question asks to implement an operator such as power, squareroot or division and want it to be faster than O(n), binary search is usually the approach to go.
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#### Some common formulas:
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- Sum of 1 to N = (n+1) \* n/2
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- Sum of GP = 2<sup>0</sup> + 2<sup>1</sup> + 2<sup>2</sup> + 2<sup>3</sup> + ... 2<sup>n</sup> = 2<sup>n+1</sup> - 1
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- Permutations of N = N! / (N-K)!
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- Combinations of N = N! / (K! \* (N-K)!)
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## Recommended LeetCode questions
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- [Pow(x, n)](https://leetcode.com/problems/powx-n/)
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- [Sqrt(x)](https://leetcode.com/problems/sqrtx/)
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- [Integer to English Words](https://leetcode.com/problems/integer-to-english-words/)
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