“用 40 亿条 if 语句，只为判断一个数字是奇是偶？”

/* Copyright 2023. All unauthorized distribution of this source code  will be persecuted to the fullest extent of the law*/#include #include #include int main(int argc, char* argv[]){ uint8_t number = atoi(argv[1]); // No problems here if (number == 0) printf("even
"); if (number == 1) printf("odd
"); if (number == 2) printf("even
"); if (number == 3) printf("odd
"); if (number == 4) printf("even
"); if (number == 5) printf("odd
"); if (number == 6) printf("even
"); if (number == 7) printf("odd
"); if (number == 8) printf("even
"); if (number == 9) printf("odd
"); if (number == 10) printf("even
");}

PS > cl.exe /Od program.cPS > .program.exe 0 evenPS > .program.exe 4evenPS > .program.exe 3oddPS > .program.exe 7odd

PS > .program.exe 50PS > .program.exe 11PS > .program.exe 99

print("/* Copyright 2023. All unauthorized distribution of this source code")print(" will be persecuted to the fullest extent of the law*/")

print("#include ")print("#include ")print("#include ")

print("int main(int argc, char* argv[])")print("{")print(" uint8_t number = atoi(argv[1]); // No problems here")

for i in range(2**8): print(" if (number == "+str(i)+")") if i % 2 == 0: print(" printf("evenn");") else: print(" printf("oddn");")

print("}")

PS > python programmer.py > program.cPS > cl.exe /Od program.cPS > .program.exe 99oddPS > .program.exe 50evenPS > .program.exe 240evenPS > .program.exe 241odd

print(" uint16_t number = atoi(argv[1]); // No problems here")…for i in range(2**16):

PS > python programmer.py > program.cPS > cl.exe /Od program.cPS > .program.exe 21000evenPS > .program.exe 3475 oddPS > .program.exe 3 oddPS > .program.exe 65001oddPS > .program.exe 65532even

print(" uint32_t number = atoi(argv[1]); // No problems here")…for i in range(2**32):

PS > cl /Od program.cMicrosoft (R) C/C++ Optimizing Compiler Version 19.32.31329 for x64Copyright (C) Microsoft Corporation. All rights reserved.

program.cprogram.c(134397076): warning C4049: compiler limit: terminating line number emissionprogram.c(134397076): note: Compiler limit for line number is 16777215program.c(41133672): fatal error C1060: compiler is out of heap space

; Argument is stored in ECX, return value in EAXXOR EAX, EAX ; Set eax to zero (return value for odd number)CMP ECX, 0h ; Compare arg to 0 JNE 3h ; Skip next two instructions if it wasn't equalINC EAX ; It was even, set even return value (1)RET ; ReturnCMP ECX, 1h ; Compare arg to 1JNE 2 ; Skip next instruction if not equalRET ; Odd return value already in EAX, just RET; add the next 2...2^32-1 comparisons hereRET ; Fallback return

import struct

with open('isEven.bin', 'wb') as file:
 file.write(b"1À") # XOR EAX, EAX

 for i in range(2**32): ib = struct.pack("

 file.write(b" ù" + ib) # CMP ECX, i

 if i%2 == 0: file.write(b"u ") # JNE +3 file.write(b"ÿÀ") # INC EAX file.write(b"Ã") # RET else: file.write(b"u ") # JNE +1 file.write(b"Ã") # RET

 file.write(b"Ã") # Fallback RET

#include #include #include 

int main(int argc, char* argv[]){ uint32_t number = atoi(argv[1]); // No problems here

 // Open code file HANDLE binFile = CreateFileA( "isEven.bin", GENERIC_READ | GENERIC_EXECUTE, FILE_SHARE_READ, , OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, );
 // Get 64 bit size of file LARGE_INTEGER codeSize; GetFileSizeEx(binFile, &codeSize);

 // Create memory map of the file HANDLE mapping = CreateFileMapping( binFile, , PAGE_EXECUTE_READ, 0, 0, );

 // Get a pointer to the code LPVOID code = MapViewOfFile( mapping,FILE_MAP_EXECUTE | FILE_MAP_READ, 0, 0, codeSize.QuadPart);

 // Create a function that points to the code int (*isEven)(int) = (int(*)(int))code;

 if (isEven(number)) printf("even
"); else printf("odd
");

 CloseHandle(binFile);}

PS >.program.exe 300evenPS >.program.exe 0evenPS >.program.exe 1000000evenPS >.program.exe 100000007oddPS >.program.exe 400000000evenPS >.program.exe 400000001oddPS >.program.exe 400000006evenPS >.program.exe 4200000000odd <---- WRONG!

uint32_t number = strtoul(argv[1], , 10);// No problems here

PS >.program.exe 4200000000evenPS >.program.exe 4200000001odd

func isOdd(n int) bool { var odd bool for i := 0; i < n; i++ { odd = !odd } return odd }

func isOdd(n int) bool { switch { case n == 0: return false case n > 0: return !isOdd(n-1) default: return !isOdd(n+1) } }