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 <stdio.h>#include <stdint.h>#include <stdlib.h>int main(int argc, char* argv[]){    uint8_t number = atoi(argv[1]); // No problems here    if (number == 0)        printf("evenn");    if (number == 1)        printf("oddn");    if (number == 2)        printf("evenn");    if (number == 3)        printf("oddn");    if (number == 4)        printf("evenn");    if (number == 5)        printf("oddn");    if (number == 6)        printf("evenn");    if (number == 7)        printf("oddn");    if (number == 8)        printf("evenn");    if (number == 9)        printf("oddn");    if (number == 10)        printf("evenn");}

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 <stdio.h>")print("#include <stdint.h>")print("#include <stdlib.h>")

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("even\n");")    else:        print("        printf("odd\n");")

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"x31xC0")                     # XOR EAX, EAX

    for i in range(2**32):        ib = struct.pack("<I", i)               # Encode i as 32 bit little endian integer

        file.write(b"x81xF9" + ib)            # CMP ECX, i

        if i%2 == 0:            file.write(b"x75x03")             # JNE +3            file.write(b"xFFxC0")             # INC EAX            file.write(b"xC3")                 # RET        else:            file.write(b"x75x01")             # JNE +1            file.write(b"xC3")                 # RET

    file.write(b"xC3")                         # Fallback RET

#include <stdio.h>#include <Windows.h>#include <stdint.h>

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,                        NULL,                        OPEN_EXISTING,                        FILE_ATTRIBUTE_NORMAL,                        NULL);
    // Get 64 bit size of file    LARGE_INTEGER codeSize;    GetFileSizeEx(binFile, &codeSize);

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

    // 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("evenn");    else        printf("oddn");

    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], NULL, 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)    }  }