11–20 of 73 posts
> I will be using x64 assembly with the AT&T syntax as it is objectively superior than the Intel syntax. This made me laugh because it must be a reference to this: https://news.ycombinator.com/item?id=33652023 > I contend that the AT&T syntax is harmful and bad, and should never be used, for any reason, under any circumstances, by anyone.
You can use the 32bit xor to reset the register. Also TEST REG,REG might be better for checking if it’s zero.
x32 converter for GNU/Linux: sed -i 's/r//g' invert_tree.asm > invet_tee.asm
It's not that easy, you also have to account for the pointer sizes (4 bytes instead of 8). Also alignment requirements are different on x32.
I love seeing people solve leetcode challenges in asm, are there any more blogposts like this?
The hard bit of solving them is usually the algorithm though - when you know that you can code it in anything.
I'm with GP, it's fun seeing how solutions differ between languages as a way to peek into other language communities I don't spend as much time in.
:invert
cmp rax, 0
jnz swap:
ret
:swap
push rax
mov rax, [rax]
call invert
mov rbx,[rsp]
xchg rax, [rbx+8]
mov [rbx], rax
call invert
pop rax
ret
EDIT: After reading the article now, that seems rather inefficient to me, to use local variables on the stack for everything. And why is the function returning a node if it is mutating the tree in place?
You can use the 32bit xor to reset the register. Also TEST REG,REG might be better for checking if it’s zero.
Is 32 bit cheaper? Still 1 cycle.
Read more here https://stackoverflow.com/questions/17981447/microarchitectu...
> [...] these zeroing instructions extremely efficient, with a throughput of four zeroing instructons per clock cycle.
Also, the xor instruction takes up the smallest amount of .text space (right?).
Similarly, the reality is that as a professional programmer you spend no time doing work like leetcode.
Instead, you spend a lot of time understanding and slightly modifying (fixing or enhancing/extending) code.
With the rise of language model code completion systems (e.g., Microsoft Copilot) even more time will be spent inspecting and understanding code to find problems.
With these facts in mind, I have been building a new form of leetcode:
Most puzzles are interesting algorithms that you will learn useful techniques from, so it's never a waste of time to think about them. And even though the bugs are all quite trivial, I can see it's very challenging for many people.
It's about half-way ready to launch, needing 30 more puzzles. I am working my way through Knuth's The Art of Programming Volume 4B and today I'll see if Algorithm X (Dancing Links Exact Cover Backtracking) can be made to fit for Bugs 38 and 39 (or whether it's too complicated).
Assume RAX points to the root node and nodes just contain two child pointers and everything is aligned and whatever. :invert cmp rax, 0 jnz swap: ret :swap push rax mov rax, [rax] call invert mov rbx,[rsp] xchg rax, [rbx+8] mov [rbx], rax call invert pop rax ret The last time I used an assembler was before x86-64 was invented, I am not even sure I ever used one in protected mode. But that seems a totally reasonable w…