Code Bot compiler - Online Compiler NASM 32. This code counts how many numbers from 1 to N have exactly K set bits (1s) in their binary representation. It uses combinatorial mathematics (combinations function) to count numbers with a specific number of bits set, rather than iterating through all n...

Online Compiler Nasm

extern io_get_udec, io_print_dec section .bss kval resd 1 zero resd 1 shablon resd 1 ostright resd 1 section .text global main main: call io_get_udec mov edi, eax ; edi = N call io_get_udec mov [kval], eax ; K xor ebx, ebx ; ebx = ans mov dword [zero], 0 mov eax, edi xor esi, esi ; esi = m bitschet: test eax, eax jz bitvse inc esi shr eax, 1 jmp bitschet bitvse: mov ecx, 1 lessN: cmp ecx, esi jae endlessN mov eax, ecx dec eax ; n = len - 1 mov edx, [kval] ; k = K push ecx call combinations pop ecx add ebx, eax inc ecx jmp lessN endlessN: mov ecx, esi cmp ecx, 1 jbe provN dec ecx mov [ostright], ecx mov eax, 1 mov ecx, esi sub ecx, 2 shl eax, cl mov [shablon], eax rasborN: mov eax, [shablon] test eax, eax jz provN test edi, eax jz found mov eax, [kval] mov edx, [zero] inc edx sub eax, edx ; need = K - (zero + 1) js next mov edx, eax ; k = need mov eax, [ostright] dec eax ; n = сколько бит справа call combinations add ebx, eax jmp next found: inc dword [zero] next: dec dword [ostright] shr dword [shablon], 1 jmp rasborN provN: mov eax, [zero] cmp eax, [kval] jne done inc ebx done: mov eax, ebx call io_print_dec xor eax, eax ret combinations: push ebx push ecx push esi push edi cmp edx, eax ja combzero cmp edx, 0 je combone mov esi, eax ; n mov ecx, edx ; k mov ebx, 1 ; result mov edi, 1 ; i combschet: cmp edi, ecx ja endcomb mov eax, esi sub eax, edi inc eax ; n - i + 1 mul ebx ; edx:eax = eax * result div edi ; eax = eax / i mov ebx, eax inc edi jmp combschet endcomb: mov eax, ebx jmp vosvrat combzero: xor eax, eax jmp vosvrat combone: mov eax, 1 vosvrat: pop edi pop esi pop ecx pop ebx ret

This code counts how many numbers from 1 to N have exactly K set bits (1s) in their binary representation. It uses combinatorial mathematics (combinations function) to count numbers with a specific number of bits set, rather than iterating through all numbers.

**Specific hints:**
1. The `combinations` function calculates C(n,k) but has a bug: it uses `div edi` without first clearing `edx`, which can cause incorrect results when the multiplication produces a value that doesn't fit in 32 bits.
2. The algorithm processes bits from most significant to least significant, but the `shablon` initialization (`mov eax, 1` then `shl eax, cl`) may not correctly mask all bit positions if N has fewer bits than expected.