Clearing Bits using BITWISE OPERATORS

[digital iron]

can only use bitwise, no ifs, no mod

[marble mauve]

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[digital iron]

ping!

[polar granite]

so would 101011 become 101000 and would 1111 become 0000 and would 10101 become 10100?

[dire jolt]

I don’t think this is possible, bit wise operations operate on individual bits so they have no way of differentiating if a bit is at the end or beginning

However if you allow yourself to use ctz (count tailing zeros), you should be able to do something like this

int n; //input
int rot_num = ctz(~n); // count trailing 1s
n >>= rot_num; // shift right
n <<= rot_num; // shift back left, replacing last rot_num bits with 0

https://en.wikipedia.org/wiki/Find_first_set

There’s an implementation here maybe you could do something

[simple pilot]

while the last bit is set, shift one to the right

done

[polar granite]

@digital iron can you use loops at all? Because internally those use if

[stable briar]

Program Output

32

Lord Dimwit Flathead#1478 | 68ms | g101 | godbolt.org

Program Output

32

Lord Dimwit Flathead#1478 | 47ms | g101 | godbolt.org

Program Output

32

Lord Dimwit Flathead#1478 | 156ms | g101 | godbolt.org

[acoustic storm]

Interesting assignment. Feels like code golf.
I cannot do it without a loop.

[dire jolt]

Wow that’s very clever

[acoustic storm]

It is. I tip my hat to thee @simple pilot
Annoyingly, I had a voice in my head telling me there is a clever solution.
I am just not clever enough to come up with it myself.
I can only marvel at its simplicity when confronted with it.

[dire jolt]

Why did it get deleted

[dire jolt]

btw the original response from 5921 was x&(x+1)

[polar granite]

Dang that's genius

[marble mauve]

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[warped prawn]

https://en.cppreference.com/w/cpp/numeric/countr_one theres also c++20 way of counting how many consecutive bits there are

https://en.cppreference.com/w/cpp/numeric/countl_one

[dire jolt]

Ah, I didn’t know c++ added that

Cool 👍

[marble mauve]

@digital iron

This question thread is being automatically closed. If your question is not answered feel free to bump the post or re-ask. Take a look at !howto ask for tips on improving your question.

[digital iron]

yep done

thanks

[marble mauve]

@digital iron Has your question been resolved? If so, run !solved :)

[digital iron]

!solved