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Adding algorithm to check if number is prime or not. #834

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omkarlanghe wants to merge 7 commits into TheAlgorithms:master from omkarlanghe:master

omkarlanghe commented Jun 7, 2020

My first contribution to this repository contains algorithm to check if the given number is prime or not.

Small description on how I have optimized the logic:

Reduced all possibilities of a number which cannot be prime.

Eg: No even number, except 2 can be a prime number, hence we will increment our loop with i+2 jumping on all odd numbers only.

If number is <= 1 or if it is even except 2, break the loop and return false telling number is not prime.


        Optimized algorithm to check if number is prime or not.

48e7510

omkarlanghe closed this

omkarlanghe reopened this

kvedala suggested changes

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kvedala left a comment

Use a simpler file name like ‘check_prime.cpp’
See #807 for how to comment your code. People should be able to read and learn from your code
Please done say ‘most optimized algorithm’ if there is no research publication backing your claim

omkarlanghe added 2 commits


        logic to check if given number is prime or not.

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        logic to check if given number is prime or not.

7986a65

omkarlanghe changed the title ~~Adding optimized algorithm to check if number is prime or not.~~ Adding algorithm to check if number is prime or not.

Author

omkarlanghe commented Jun 7, 2020

@kvedala Modified the code as per the changes you have suggested.

Contributor

kvedala commented Jun 7, 2020

@kvedala Modified the code as per the changes you have suggested.

Please see the files changes in #807 - The comment blocks, and structure is per the doxygen standard. link to actual file

GCC suggests -

$ g++ math/check_prime.cpp -o test -Wall
math/check_prime.cpp: In function 'int is_prime(int)':
math/check_prime.cpp:8:23: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
    8 |     } else if (no & 1 == 0) {  // otherwise if other even numbers, return false

Also, if you want to optimize further, you can have the line# 12 loop condition to go only till (I*i) < no - again, this already exists in some of the existing code in the repository.


        logic to check if given number is prime or not.

6d75335

kvedala reviewed

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        logic to check if given number is prime or not.

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kvedala approved these changes

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kvedala left a comment •

edited

good efforts. Documentation is still not upto standard - not all functions are documented. Please see #807 as referenced above.


        Included appropriate comments as per standards.

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kvedala approved these changes

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kvedala left a comment

👍

ayaankhan98 reviewed

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Panquesito7 reviewed

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        variable name renamed to num

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ayaankhan98 reviewed

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ayaankhan98 left a comment

looks good

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