很简单。一个整型数据。
不使用循环，不使用If，将其逆序输出。
例如：
输入：124578
输出：875421
不知道能实现么，兄弟们讨论下！
那天看了shoooo回的一个逆序输出的题目，
有点启发，后来想这个题目用类似的思路作，
试了下，好像不行！
- 标 题： 来个简单题目，看哪位兄弟写的最好！
- 作 者：壹只老虎
- 时 间：2007-04-08 20:22
- 链 接：http://bbs.pediy.com/showthread.php?t=42354
很简单。一个整型数据。
不使用循环，不使用If，将其逆序输出。
例如：
输入：124578
输出：875421
不知道能实现么，兄弟们讨论下！
那天看了shoooo回的一个逆序输出的题目，
有点启发，后来想这个题目用类似的思路作，
试了下，好像不行！
题目要求输入是整型，最大长度有限制，那就可以玩体力活了
负数的不要了
#include <stdio.h>
#include <math.h>
void IntRev(int x,char *szOut)
{
int n;
n = (int)log10(x);
szOut[0] = x%10 + 0x30;
x /= 10;
szOut[1] = x%10 + 0x30;
x /= 10;
szOut[2] = x%10 + 0x30;
x /= 10;
szOut[3] = x%10 + 0x30;
x /= 10;
szOut[4] = x%10 + 0x30;
x /= 10;
szOut[5] = x%10 + 0x30;
x /= 10;
szOut[6] = x%10 + 0x30;
x /= 10;
szOut[7] = x%10 + 0x30;
x /= 10;
szOut[8] = x%10 + 0x30;
x /= 10;
szOut[9] = x%10 + 0x30;
szOut[n+1] = 0;
}
int main()
{
char szOut[20];
int x = 2147483647;
IntRev(x,szOut);
printf(szOut);
return 0;
}
VC6，位数不限（不过当然要求输入和输出值都小于2的32次方），从最高位开始转换
#pragma optimize("",off)
unsigned int reva(unsigned int a)
{
unsigned int f2=1000000000;
unsigned int f1=1;
return (((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10))&&((!(a/f2))&&(f2/=10)&&(f1*=10)))*0+((f1=f2)*0+(f2=1)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1);
}
int main(int argc, char* argv[])
{
printf("%u %u %u\r\n",reva(1234567893),reva(12345),reva(0));
return 0;
}
输出：
3987654321 54321 0
Press any key to continue
我想出一个方法:
整数:
字符串:代码:#include<stdio.h> int revd(unsigned u) { return u&&(printf("%u",u%10),revd(u/10)); } int main() { return revd(123456789); }
也许还有更简单的吧...代码:#include<stdio.h> int revs(char *p) { return *p&&printf("%c",*p,revs(p+1)); } int main() { return revs("123456789"); }
最后给出一个直接返回整数的版本:
代码:unsigned revd(unsigned u,unsigned t=0) { return (!(u&&!(t=revd(u/10,t*10+u%10))))*t; } int main() { return printf("%u\n",revd(123456789)); }
回楼上，push/pop本质上只是数据传送语句，和mov[esp],X;add esp,4;并无不同
用&&跳过执行，在ASM里仍有跳转语句，改进一下：
#pragma optimize("",off)
unsigned int reva(unsigned int a)
{
unsigned int f2=1000000000;
unsigned int f1=1;
return ((f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f2/=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1))+(f1*=((((a+(a-1)/(-1))/f2-1)/(-1))*9+1)))*0+((f1=f2)*0+(f2=1)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1+(f1/=10)*0+(f2*=10)*0+((a/f2)%10)*f1);
}
int main(int argc, char* argv[])
{
printf("%u %u %u %u %u\r\n",reva(1234567893),reva(12345),reva(1),reva(4294967293),reva(0));
return 0;
}
输出：
3987654321 54321 1 3927694924 0
Press any key to continue
纯算术运算，在汇编里没有跳转：
.text:00401000 sub_401000 proc near ; CODE XREF: _main+5p
.text:00401000 ; _main+10p ...
.text:00401000
.text:00401000 f1 = dword ptr -8
.text:00401000 f2 = dword ptr -4
.text:00401000 a = dword ptr 8
.text:00401000
.text:00401000 push ebp
.text:00401001 mov ebp, esp
.text:00401003 sub esp, 8
.text:00401006 push esi
.text:00401007 mov [ebp+f2], 3B9ACA00h
.text:0040100E mov [ebp+f1], 1
.text:00401015 mov eax, [ebp+a]
.text:00401018 sub eax, 1
.text:0040101B xor edx, edx
.text:0040101D or ecx, 0FFFFFFFFh
.text:00401020 div ecx
.text:00401022 mov edx, [ebp+a]
.text:00401025 add eax, edx
.text:00401027 xor edx, edx
.text:00401029 div [ebp+f2]
.text:0040102C sub eax, 1
.text:0040102F xor edx, edx
.text:00401031 or ecx, 0FFFFFFFFh
.text:00401034 div ecx
.text:00401036 mov ecx, eax
.text:00401038 imul ecx, 9
.text:0040103B add ecx, 1
.text:0040103E mov eax, [ebp+f2]
.text:00401041 xor edx, edx
.text:00401043 div ecx
.text:00401045 mov [ebp+f2], eax
.text:00401048 mov eax, [ebp+a]
.text:0040104B sub eax, 1
.text:0040104E xor edx, edx
.text:00401050 or ecx, 0FFFFFFFFh
.text:00401053 div ecx
.text:00401055 mov edx, [ebp+a]
.text:00401058 add eax, edx
.text:0040105A xor edx, edx
.text:0040105C div [ebp+f2]
.text:0040105F sub eax, 1
.text:00401062 xor edx, edx
.text:00401064 or ecx, 0FFFFFFFFh
.text:00401067 div ecx
.text:00401069 imul eax, 9
.text:0040106C add eax, 1
.text:0040106F mov edx, [ebp+f1]
.text:00401072 imul edx, eax
.text:00401075 mov [ebp+f1], edx
.text:00401078 mov eax, [ebp+a]
.text:0040107B sub eax, 1
.text:0040107E xor edx, edx
.text:00401080 or ecx, 0FFFFFFFFh
.text:00401083 div ecx
.text:00401085 mov edx, [ebp+a]
.text:00401088 add eax, edx
.text:0040108A xor edx, edx
.text:0040108C div [ebp+f2]
.text:0040108F sub eax, 1
.text:00401092 xor edx, edx
.text:00401094 or ecx, 0FFFFFFFFh
.text:00401097 div ecx
.text:00401099 mov ecx, eax
.text:0040109B imul ecx, 9
.text:0040109E add ecx, 1
.text:004010A1 mov eax, [ebp+f2]
.text:004010A4 xor edx, edx
.text:004010A6 div ecx
.text:004010A8 mov [ebp+f2], eax
.text:004010AB mov eax, [ebp+a]
.text:004010AE sub eax, 1
.text:004010B1 xor edx, edx
.text:004010B3 or ecx, 0FFFFFFFFh
.text:004010B6 div ecx
.text:004010B8 mov edx, [ebp+a]
.text:004010BB add eax, edx
.text:004010BD xor edx, edx
.text:004010BF div [ebp+f2]
.text:004010C2 sub eax, 1
.text:004010C5 xor edx, edx
.text:004010C7 or ecx, 0FFFFFFFFh
.text:004010CA div ecx
.text:004010CC imul eax, 9
.text:004010CF add eax, 1
.text:004010D2 mov edx, [ebp+f1]
.text:004010D5 imul edx, eax
.text:004010D8 mov [ebp+f1], edx
.text:004010DB mov eax, [ebp+a]
.text:004010DE sub eax, 1
.text:004010E1 xor edx, edx
.text:004010E3 or ecx, 0FFFFFFFFh
.text:004010E6 div ecx
.text:004010E8 mov edx, [ebp+a]
.text:004010EB add eax, edx
.text:004010ED xor edx, edx
.text:004010EF div [ebp+f2]
.text:004010F2 sub eax, 1
.text:004010F5 xor edx, edx
.text:004010F7 or ecx, 0FFFFFFFFh
.text:004010FA div ecx
.text:004010FC mov ecx, eax
.text:004010FE imul ecx, 9
.text:00401101 add ecx, 1
.text:00401104 mov eax, [ebp+f2]
.text:00401107 xor edx, edx
.text:00401109 div ecx
.text:0040110B mov [ebp+f2], eax
.text:0040110E mov eax, [ebp+a]
.text:00401111 sub eax, 1
.text:00401114 xor edx, edx
.text:00401116 or ecx, 0FFFFFFFFh
.text:00401119 div ecx
.text:0040111B mov edx, [ebp+a]
.text:0040111E add eax, edx
.text:00401120 xor edx, edx
.text:00401122 div [ebp+f2]
.text:00401125 sub eax, 1
.text:00401128 xor edx, edx
.text:0040112A or ecx, 0FFFFFFFFh
.text:0040112D div ecx
.text:0040112F imul eax, 9
.text:00401132 add eax, 1
.text:00401135 mov edx, [ebp+f1]
.text:00401138 imul edx, eax
.text:0040113B mov [ebp+f1], edx
.text:0040113E mov eax, [ebp+a]
.text:00401141 sub eax, 1
.text:00401144 xor edx, edx
.text:00401146 or ecx, 0FFFFFFFFh
.text:00401149 div ecx
.text:0040114B mov edx, [ebp+a]
.text:0040114E add eax, edx
.text:00401150 xor edx, edx
.text:00401152 div [ebp+f2]
.text:00401155 sub eax, 1
.text:00401158 xor edx, edx
.text:0040115A or ecx, 0FFFFFFFFh
.text:0040115D div ecx
.text:0040115F mov ecx, eax
.text:00401161 imul ecx, 9
.text:00401164 add ecx, 1
.text:00401167 mov eax, [ebp+f2]
.text:0040116A xor edx, edx
.text:0040116C div ecx
.text:0040116E mov [ebp+f2], eax
.text:00401171 mov eax, [ebp+a]
.text:00401174 sub eax, 1
.text:00401177 xor edx, edx
.text:00401179 or ecx, 0FFFFFFFFh
.text:0040117C div ecx
.text:0040117E mov edx, [ebp+a]
.text:00401181 add eax, edx
.text:00401183 xor edx, edx
.text:00401185 div [ebp+f2]
.text:00401188 sub eax, 1
.text:0040118B xor edx, edx
.text:0040118D or ecx, 0FFFFFFFFh
.text:00401190 div ecx
.text:00401192 imul eax, 9
.text:00401195 add eax, 1
.text:00401198 mov edx, [ebp+f1]
.text:0040119B imul edx, eax
.text:0040119E mov [ebp+f1], edx
.text:004011A1 mov eax, [ebp+a]
.text:004011A4 sub eax, 1
.text:004011A7 xor edx, edx
.text:004011A9 or ecx, 0FFFFFFFFh
.text:004011AC div ecx
.text:004011AE mov edx, [ebp+a]
.text:004011B1 add eax, edx
.text:004011B3 xor edx, edx
.text:004011B5 div [ebp+f2]
.text:004011B8 sub eax, 1
.text:004011BB xor edx, edx
.text:004011BD or ecx, 0FFFFFFFFh
.text:004011C0 div ecx
.text:004011C2 mov ecx, eax
.text:004011C4 imul ecx, 9
.text:004011C7 add ecx, 1
.text:004011CA mov eax, [ebp+f2]
.text:004011CD xor edx, edx
.text:004011CF div ecx
.text:004011D1 mov [ebp+f2], eax
.text:004011D4 mov eax, [ebp+a]
.text:004011D7 sub eax, 1
.text:004011DA xor edx, edx
.text:004011DC or ecx, 0FFFFFFFFh
.text:004011DF div ecx
.text:004011E1 mov edx, [ebp+a]
.text:004011E4 add eax, edx
.text:004011E6 xor edx, edx
.text:004011E8 div [ebp+f2]
.text:004011EB sub eax, 1
.text:004011EE xor edx, edx
.text:004011F0 or ecx, 0FFFFFFFFh
.text:004011F3 div ecx
.text:004011F5 imul eax, 9
.text:004011F8 add eax, 1
.text:004011FB mov edx, [ebp+f1]
.text:004011FE imul edx, eax
.text:00401201 mov [ebp+f1], edx
.text:00401204 mov eax, [ebp+a]
.text:00401207 sub eax, 1
.text:0040120A xor edx, edx
.text:0040120C or ecx, 0FFFFFFFFh
.text:0040120F div ecx
.text:00401211 mov edx, [ebp+a]
.text:00401214 add eax, edx
.text:00401216 xor edx, edx
.text:00401218 div [ebp+f2]
.text:0040121B sub eax, 1
.text:0040121E xor edx, edx
.text:00401220 or ecx, 0FFFFFFFFh
.text:00401223 div ecx
.text:00401225 mov ecx, eax
.text:00401227 imul ecx, 9
.text:0040122A add ecx, 1
.text:0040122D mov eax, [ebp+f2]
.text:00401230 xor edx, edx
.text:00401232 div ecx
.text:00401234 mov [ebp+f2], eax
.text:00401237 mov eax, [ebp+a]
.text:0040123A sub eax, 1
.text:0040123D xor edx, edx
.text:0040123F or ecx, 0FFFFFFFFh
.text:00401242 div ecx
.text:00401244 mov edx, [ebp+a]
.text:00401247 add eax, edx
.text:00401249 xor edx, edx
.text:0040124B div [ebp+f2]
.text:0040124E sub eax, 1
.text:00401251 xor edx, edx
.text:00401253 or ecx, 0FFFFFFFFh
.text:00401256 div ecx
.text:00401258 imul eax, 9
.text:0040125B add eax, 1
.text:0040125E mov edx, [ebp+f1]
.text:00401261 imul edx, eax
.text:00401264 mov [ebp+f1], edx
.text:00401267 mov eax, [ebp+a]
.text:0040126A sub eax, 1
.text:0040126D xor edx, edx
.text:0040126F or ecx, 0FFFFFFFFh
.text:00401272 div ecx
.text:00401274 mov edx, [ebp+a]
.text:00401277 add eax, edx
.text:00401279 xor edx, edx
.text:0040127B div [ebp+f2]
.text:0040127E sub eax, 1
.text:00401281 xor edx, edx
.text:00401283 or ecx, 0FFFFFFFFh
.text:00401286 div ecx
.text:00401288 mov ecx, eax
.text:0040128A imul ecx, 9
.text:0040128D add ecx, 1
.text:00401290 mov eax, [ebp+f2]
.text:00401293 xor edx, edx
.text:00401295 div ecx
.text:00401297 mov [ebp+f2], eax
.text:0040129A mov eax, [ebp+a]
.text:0040129D sub eax, 1
.text:004012A0 xor edx, edx
.text:004012A2 or ecx, 0FFFFFFFFh
.text:004012A5 div ecx
.text:004012A7 mov edx, [ebp+a]
.text:004012AA add eax, edx
.text:004012AC xor edx, edx
.text:004012AE div [ebp+f2]
.text:004012B1 sub eax, 1
.text:004012B4 xor edx, edx
.text:004012B6 or ecx, 0FFFFFFFFh
.text:004012B9 div ecx
.text:004012BB imul eax, 9
.text:004012BE add eax, 1
.text:004012C1 mov edx, [ebp+f1]
.text:004012C4 imul edx, eax
.text:004012C7 mov [ebp+f1], edx
.text:004012CA mov eax, [ebp+a]
.text:004012CD sub eax, 1
.text:004012D0 xor edx, edx
.text:004012D2 or ecx, 0FFFFFFFFh
.text:004012D5 div ecx
.text:004012D7 mov edx, [ebp+a]
.text:004012DA add eax, edx
.text:004012DC xor edx, edx
.text:004012DE div [ebp+f2]
.text:004012E1 sub eax, 1
.text:004012E4 xor edx, edx
.text:004012E6 or ecx, 0FFFFFFFFh
.text:004012E9 div ecx
.text:004012EB mov ecx, eax
.text:004012ED imul ecx, 9
.text:004012F0 add ecx, 1
.text:004012F3 mov eax, [ebp+f2]
.text:004012F6 xor edx, edx
.text:004012F8 div ecx
.text:004012FA mov [ebp+f2], eax
.text:004012FD mov eax, [ebp+a]
.text:00401300 sub eax, 1
.text:00401303 xor edx, edx
.text:00401305 or ecx, 0FFFFFFFFh
.text:00401308 div ecx
.text:0040130A mov edx, [ebp+a]
.text:0040130D add eax, edx
.text:0040130F xor edx, edx
.text:00401311 div [ebp+f2]
.text:00401314 sub eax, 1
.text:00401317 xor edx, edx
.text:00401319 or ecx, 0FFFFFFFFh
.text:0040131C div ecx
.text:0040131E imul eax, 9
.text:00401321 add eax, 1
.text:00401324 mov edx, [ebp+f1]
.text:00401327 imul edx, eax
.text:0040132A mov [ebp+f1], edx
.text:0040132D mov eax, [ebp+a]
.text:00401330 sub eax, 1
.text:00401333 xor edx, edx
.text:00401335 or ecx, 0FFFFFFFFh
.text:00401338 div ecx
.text:0040133A mov edx, [ebp+a]
.text:0040133D add eax, edx
.text:0040133F xor edx, edx
.text:00401341 div [ebp+f2]
.text:00401344 sub eax, 1
.text:00401347 xor edx, edx
.text:00401349 or ecx, 0FFFFFFFFh
.text:0040134C div ecx
.text:0040134E mov ecx, eax
.text:00401350 imul ecx, 9
.text:00401353 add ecx, 1
.text:00401356 mov eax, [ebp+f2]
.text:00401359 xor edx, edx
.text:0040135B div ecx
.text:0040135D mov [ebp+f2], eax
.text:00401360 mov eax, [ebp+a]
.text:00401363 sub eax, 1
.text:00401366 xor edx, edx
.text:00401368 or ecx, 0FFFFFFFFh
.text:0040136B div ecx
.text:0040136D mov edx, [ebp+a]
.text:00401370 add eax, edx
.text:00401372 xor edx, edx
.text:00401374 div [ebp+f2]
.text:00401377 sub eax, 1
.text:0040137A xor edx, edx
.text:0040137C or ecx, 0FFFFFFFFh
.text:0040137F div ecx
.text:00401381 imul eax, 9
.text:00401384 add eax, 1
.text:00401387 mov edx, [ebp+f1]
.text:0040138A imul edx, eax
.text:0040138D mov [ebp+f1], edx
.text:00401390 mov eax, [ebp+a]
.text:00401393 sub eax, 1
.text:00401396 xor edx, edx
.text:00401398 or ecx, 0FFFFFFFFh
.text:0040139B div ecx
.text:0040139D mov edx, [ebp+a]
.text:004013A0 add eax, edx
.text:004013A2 xor edx, edx
.text:004013A4 div [ebp+f2]
.text:004013A7 sub eax, 1
.text:004013AA xor edx, edx
.text:004013AC or ecx, 0FFFFFFFFh
.text:004013AF div ecx
.text:004013B1 mov ecx, eax
.text:004013B3 imul ecx, 9
.text:004013B6 add ecx, 1
.text:004013B9 mov eax, [ebp+f2]
.text:004013BC xor edx, edx
.text:004013BE div ecx
.text:004013C0 mov [ebp+f2], eax
.text:004013C3 mov eax, [ebp+a]
.text:004013C6 sub eax, 1
.text:004013C9 xor edx, edx
.text:004013CB or ecx, 0FFFFFFFFh
.text:004013CE div ecx
.text:004013D0 mov edx, [ebp+a]
.text:004013D3 add eax, edx
.text:004013D5 xor edx, edx
.text:004013D7 div [ebp+f2]
.text:004013DA sub eax, 1
.text:004013DD xor edx, edx
.text:004013DF or ecx, 0FFFFFFFFh
.text:004013E2 div ecx
.text:004013E4 imul eax, 9
.text:004013E7 add eax, 1
.text:004013EA mov edx, [ebp+f1]
.text:004013ED imul edx, eax
.text:004013F0 mov [ebp+f1], edx
.text:004013F3 mov eax, [ebp+f2]
.text:004013F6 mov [ebp+f1], eax
.text:004013F9 mov [ebp+f2], 1
.text:00401400 mov eax, [ebp+a]
.text:00401403 xor edx, edx
.text:00401405 div [ebp+f2]
.text:00401408 xor edx, edx
.text:0040140A mov ecx, 0Ah
.text:0040140F div ecx
.text:00401411 mov ecx, edx
.text:00401413 imul ecx, [ebp+f1]
.text:00401417 mov eax, [ebp+f1]
.text:0040141A xor edx, edx
.text:0040141C mov esi, 0Ah
.text:00401421 div esi
.text:00401423 mov [ebp+f1], eax
.text:00401426 mov edx, [ebp+f2]
.text:00401429 imul edx, 0Ah
.text:0040142C mov [ebp+f2], edx
.text:0040142F mov eax, [ebp+a]
.text:00401432 xor edx, edx
.text:00401434 div [ebp+f2]
.text:00401437 xor edx, edx
.text:00401439 mov esi, 0Ah
.text:0040143E div esi
.text:00401440 imul edx, [ebp+f1]
.text:00401444 add ecx, edx
.text:00401446 mov eax, [ebp+f1]
.text:00401449 xor edx, edx
.text:0040144B mov esi, 0Ah
.text:00401450 div esi
.text:00401452 mov [ebp+f1], eax
.text:00401455 mov eax, [ebp+f2]
.text:00401458 imul eax, 0Ah
.text:0040145B mov [ebp+f2], eax
.text:0040145E mov eax, [ebp+a]
.text:00401461 xor edx, edx
.text:00401463 div [ebp+f2]
.text:00401466 xor edx, edx
.text:00401468 mov esi, 0Ah
.text:0040146D div esi
.text:0040146F imul edx, [ebp+f1]
.text:00401473 add ecx, edx
.text:00401475 mov eax, [ebp+f1]
.text:00401478 xor edx, edx
.text:0040147A mov esi, 0Ah
.text:0040147F div esi
.text:00401481 mov [ebp+f1], eax
.text:00401484 mov edx, [ebp+f2]
.text:00401487 imul edx, 0Ah
.text:0040148A mov [ebp+f2], edx
.text:0040148D mov eax, [ebp+a]
.text:00401490 xor edx, edx
.text:00401492 div [ebp+f2]
.text:00401495 xor edx, edx
.text:00401497 mov esi, 0Ah
.text:0040149C div esi
.text:0040149E imul edx, [ebp+f1]
.text:004014A2 add ecx, edx
.text:004014A4 mov eax, [ebp+f1]
.text:004014A7 xor edx, edx
.text:004014A9 mov esi, 0Ah
.text:004014AE div esi
.text:004014B0 mov [ebp+f1], eax
.text:004014B3 mov eax, [ebp+f2]
.text:004014B6 imul eax, 0Ah
.text:004014B9 mov [ebp+f2], eax
.text:004014BC mov eax, [ebp+a]
.text:004014BF xor edx, edx
.text:004014C1 div [ebp+f2]
.text:004014C4 xor edx, edx
.text:004014C6 mov esi, 0Ah
.text:004014CB div esi
.text:004014CD imul edx, [ebp+f1]
.text:004014D1 add ecx, edx
.text:004014D3 mov eax, [ebp+f1]
.text:004014D6 xor edx, edx
.text:004014D8 mov esi, 0Ah
.text:004014DD div esi
.text:004014DF mov [ebp+f1], eax
.text:004014E2 mov edx, [ebp+f2]
.text:004014E5 imul edx, 0Ah
.text:004014E8 mov [ebp+f2], edx
.text:004014EB mov eax, [ebp+a]
.text:004014EE xor edx, edx
.text:004014F0 div [ebp+f2]
.text:004014F3 xor edx, edx
.text:004014F5 mov esi, 0Ah
.text:004014FA div esi
.text:004014FC imul edx, [ebp+f1]
.text:00401500 add ecx, edx
.text:00401502 mov eax, [ebp+f1]
.text:00401505 xor edx, edx
.text:00401507 mov esi, 0Ah
.text:0040150C div esi
.text:0040150E mov [ebp+f1], eax
.text:00401511 mov eax, [ebp+f2]
.text:00401514 imul eax, 0Ah
.text:00401517 mov [ebp+f2], eax
.text:0040151A mov eax, [ebp+a]
.text:0040151D xor edx, edx
.text:0040151F div [ebp+f2]
.text:00401522 xor edx, edx
.text:00401524 mov esi, 0Ah
.text:00401529 div esi
.text:0040152B imul edx, [ebp+f1]
.text:0040152F add ecx, edx
.text:00401531 mov eax, [ebp+f1]
.text:00401534 xor edx, edx
.text:00401536 mov esi, 0Ah
.text:0040153B div esi
.text:0040153D mov [ebp+f1], eax
.text:00401540 mov edx, [ebp+f2]
.text:00401543 imul edx, 0Ah
.text:00401546 mov [ebp+f2], edx
.text:00401549 mov eax, [ebp+a]
.text:0040154C xor edx, edx
.text:0040154E div [ebp+f2]
.text:00401551 xor edx, edx
.text:00401553 mov esi, 0Ah
.text:00401558 div esi
.text:0040155A imul edx, [ebp+f1]
.text:0040155E add ecx, edx
.text:00401560 mov eax, [ebp+f1]
.text:00401563 xor edx, edx
.text:00401565 mov esi, 0Ah
.text:0040156A div esi
.text:0040156C mov [ebp+f1], eax
.text:0040156F mov eax, [ebp+f2]
.text:00401572 imul eax, 0Ah
.text:00401575 mov [ebp+f2], eax
.text:00401578 mov eax, [ebp+a]
.text:0040157B xor edx, edx
.text:0040157D div [ebp+f2]
.text:00401580 xor edx, edx
.text:00401582 mov esi, 0Ah
.text:00401587 div esi
.text:00401589 imul edx, [ebp+f1]
.text:0040158D add ecx, edx
.text:0040158F mov eax, [ebp+f1]
.text:00401592 xor edx, edx
.text:00401594 mov esi, 0Ah
.text:00401599 div esi
.text:0040159B mov [ebp+f1], eax
.text:0040159E mov edx, [ebp+f2]
.text:004015A1 imul edx, 0Ah
.text:004015A4 mov [ebp+f2], edx
.text:004015A7 mov eax, [ebp+a]
.text:004015AA xor edx, edx
.text:004015AC div [ebp+f2]
.text:004015AF xor edx, edx
.text:004015B1 mov esi, 0Ah
.text:004015B6 div esi
.text:004015B8 imul edx, [ebp+f1]
.text:004015BC add ecx, edx
.text:004015BE mov eax, ecx
.text:004015C0 pop esi
.text:004015C1 mov esp, ebp
.text:004015C3 pop ebp
.text:004015C4 retn
.text:004015C4 sub_401000 endp
不能用汇编吗，楼上的太恐怖了～～～
eax是输入，ebx是输出
MOV EAX,124578
XOR EBX,EBX
ROR EAX,14
MOV BL,AL
ROR EBX,4
ROL EAX,4
MOV BL,AL
ROL EAX,4
ROR EBX,4
MOV BL,AL
ROR EBX,4
ROL EAX,4
MOV BL,AL
ROL EAX,4
ROR EBX,4
MOV BL,AL
ROR EBX,4
ROL EAX,4
MOV BL,AL
ROL EAX,4
ROR EBX,4
XOR BL,BL
这个通用性比较强:
MOV EAX,124578
XOR EBX,EBX
ROL EAX,4
push offset DONE
push offset LOOP
ret
ret
nop
nop
nop
nop
nop
nop
LOOP:
MOV BL,AL
ROL EAX,4
ROR EBX,4
sub esp,4
dec byte ptr [esp]
ret
DONE:
AND AL,0F
AND BL,0F0
OR BL,AL
ROR EBX,4
用nop的长度来控制循环的次数，nop的次数是转换的位数-2
Try compile the following code under VS2005, with /W4 warning level,for x86
逆序输出16进制和10进制数，不能使用循环和If，无非是更麻烦一些而已：
// reverse 0x89ABCDEF to 0xFEDCBA98
VOID SwapIt( LPBYTE b1, LPBYTE b2 )
{
BYTE b = *b1;
*b1 = (*b2)<<4 + (*b2)>>4;
*b2 = b<<4 + b>>4;
}
HRESULT ReverseInt_Hex( LPDWORD pInt, LPDWORD pdwResult )
{
DWORD i = 0;
LPBYTE p = NULL;
/*
if( NULL == pInt ) well, since we CANNOT use if, assume the parameter is valid here
return E_INVALIDARG;
*/
i = *pInt;
p = (LPBYTE) &i;
SwapIt( p[0], p[3] );
SwapIt( p[1], p[2] );
*pdwResult = i;
return S_OK;
}
// since 0xFFFFffff = 4294967295, there are 10 digits at most for a decimal unsigned integer
// e.g. reverse 12345678 to 87654321
HRESULT ReverseInt_Decimal( LPDWORD pInt, LPDWORD pdwResult )
{
DWORD i = 0;
DWORD j = 0;
BYTE k[10] = {0}; // stores the digits, from left to right
/*
if( NULL == pInt ) again, we trust you, man :-)
return E_INVALIDARG;
*/
i = *pInt;
k[0] = i / 1000000000; j = i - k[0] * 1000000000;
k[1] = j / 100000000; j-= k[1] * 100000000;
k[2] = j / 10000000; j-= k[2] * 10000000;
k[3] = j / 1000000; j-= k[3] * 1000000;
k[4] = j / 100000; j-= k[4] * 100000;
k[5] = j / 10000; j-= k[5] * 10000;
k[6] = j / 1000; j-= k[6] * 1000;
k[7] = j / 100; j-= k[7] * 100;
k[8] = j / 10; j-= k[8] * 10;
k[9] = j;
*pdwResult = k[9] * 1000000000 +
k[8] * 100000000 +
k[7] * 10000000 +
k[6] * 1000000 +
k[5] * 100000 +
k[4] * 10000 +
k[3] * 1000 +
k[2] * 100 +
k[1] * 10 +
k[0];
return S_OK;
}
看我这个,我写的strrev,表面上没有判断指令的,使用了循环,但是还是没有使用jmp 而是用push ret,这样至少在心里上好受点,因为没有循环的世界和没有if的世界一样不好受,除非你的内存可以无限的大,我的例子中没有使用if指令,而是使用了%来判断字串结束否,其实也是一种if,但是很不明显而已,没有长度限制
void __declspec(naked) __stdcall mystrrev(const char* p_str)
{
__asm
{
mov eax,dword ptr [esp+4]
pushad
pushfd
push eax
call l_kernel
pop eax
popfd
popad
retn 4
l_kernel:
mov edi, dword ptr [esp+4]
xor eax, eax
mov ecx, -1
repne scas byte ptr es:[edi]
neg ecx
dec ecx
dec ecx
mov eax, ecx
xor edx, edx
mov ebx, 2
div ebx
add edx, eax
mov ebx, edx
call l_Loop
retn
dec ebx
l_Loop:
xor edx, edx
mov eax, 1
div ebx
mov esi, dword ptr [esp+8]
mov al, byte ptr [ecx+esi-1]
neg ecx
mov ah, byte ptr [ecx+edi-1]
mov byte ptr [ecx+edi-1], al
neg ecx
mov byte ptr [ecx+esi-1], ah
dec ecx
mov esi, dword ptr [esp]
add esi, edx
push esi
retn
}
}
int _tmain(int argc, _TCHAR* argv[])
{
char p_sTest[] = "123456789abcdefghijklmnopqrstuvwxyz";
puts(p_sTest);
mystrrev(p_sTest);
puts(p_sTest);
gets(p_sTest);
return 0;
}
TC 2.0 pass
用28楼dwing的方法改了上面的代码