来看看这是怎么回事:printf("abcdefghijklmnopqrstuvwxyz\n"+i);

SolidRabbit 2003-10-20 06:01:00
main()
{int i;

for(i = 0;i <= 26;i++)
printf("abcdefghijklmnopqrstuvwxyz\n"+i);
getch();
}


printf还有这种用法,真奇怪,我好像没在教程上看过,谁解释一下。
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administractor 2003-10-20
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我还不知道呢,有点收获。
yizhili 2003-10-20
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要学会举一反三,也要记清C中字符串与字符指针的关系。

另外请别人帮忙好歹也给点分啊。
antijpn 2003-10-20
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哦,原来是不断的将指针向后偏移
Wolf0403 2003-10-20
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不过尔尔。
写明白了就是
int main(void)
{
int i = 0;
const char * s = "abcdefghijklmnopqrstuvwxyz";
while (*s++)
printf("%s\n", s);
}
Caoyu015 2003-10-20
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"abcdefghijklmnopqrstuvwxyz\n"+i //字符串常量在 C中相当于const 指针。

TianGuangZao 2003-10-20
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abcdefghijklmnopqrstuvwxyz
bcdefghijklmnopqrstuvwxyz
cdefghijklmnopqrstuvwxyz
defghijklmnopqrstuvwxyz
efghijklmnopqrstuvwxyz
fghijklmnopqrstuvwxyz
ghijklmnopqrstuvwxyz
hijklmnopqrstuvwxyz
ijklmnopqrstuvwxyz
jklmnopqrstuvwxyz
klmnopqrstuvwxyz
lmnopqrstuvwxyz
mnopqrstuvwxyz
nopqrstuvwxyz
opqrstuvwxyz
pqrstuvwxyz
qrstuvwxyz
rstuvwxyz
stuvwxyz
tuvwxyz
uvwxyz
vwxyz
wxyz
xyz
yz
z

酷毙。
SolidRabbit 2003-10-20
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??????????
MD5加密算法(Java版) 可以运行 原理   对MD5算法简要的叙述可以为:MD5以512位分组来处理输入的信息,且每一分组又被划分为16个32位子分组,经过了一系列的处理后,算法的输出由四个32位分组组成,将这四个32位分组级联后将生成一个128位散列值。   在MD5算法中,首先需要对信息进行填充,使其位长对512求余的结果等于448。因此,信息的位长(Bits Length)将被扩展至N*512+448,N为一个非负整数,N可以是零。填充的方法如下,在信息的后面填充一个1和无数个0,直到满足上面的条件时才停止用0对信息的填充。然后,在这个结果后面附加一个以64位二进制表示的填充前信息长度。经过这两步的处理,现在的信息的位长=N*512+448+64=(N+1)*512,即长度恰好是512的整数倍。这样做的原因是为满足后面处理中对信息长度的要求。   MD5中有四个32位被称作链接变量(Chaining Variable)的整数参数,他们分别为:A=0x67452301,B=0xefcdab89,C=0x98badcfe,D=0x10325476。   当设置好这四个链接变量后,就开始进入算法的四轮循环运算。循环的次数是信息中512位信息分组的数目。   将上面四个链接变量复制到另外四个变量中:A到a,B到b,C到c,D到d。   主循环有四轮(MD4只有三轮),每轮循环都很相似。第一轮进行16次操作。每次操作对a、b、c和d中的其中三个作一次非线性函数运算,然后将所得结果加上第四个变量,文本的一个子分组和一个常数。再将所得结果向左环移一个不定的数,并加上a、b、c或d中之一。最后用该结果取代a、b、c或d中之一。   以一下是每次操作中用到的四个非线性函数(每轮一个)。   F(X,Y,Z) =(X&Y)|((~X)&Z)   G(X,Y,Z) =(X&Z)|(Y&(~Z))   H(X,Y,Z) =X^Y^Z   I(X,Y,Z)=Y^(X|(~Z))   (&是与,|是或,~是非,^是异或)   这四个函数的说明:如果X、Y和Z的对应位是独立和均匀的,那么结果的每一位也应是独立和均匀的。   F是一个逐位运算的函数。即,如果X,那么Y,否则Z。函数H是逐位奇偶操作符。   假设Mj表示消息的第j个子分组(从0到15), 常数ti是4294967296*abs(sin(i))的整数部分,i取值从1到64,单位是弧度。(4294967296等于2的32次方)   FF(a, b, c, d, Mj, s, ti)表示 a = b + ((a + F(b, c, d) + Mj + ti) << s)   GG(a, b, c, d, Mj, s, ti)表示 a = b + ((a + G(b, c, d) + Mj + ti) << s)   HH(a, b, c, d, Mj, s, ti)表示 a = b + ((a + H(b, c, d) + Mj + ti) << s)   II(a, b, c, d, Mj, s, ti)表示 a = b + ((a + I(b, c, d) + Mj + ti) << s)   这四轮(64步)是:   第一轮   FF(a, b, c, d, M0, 7, 0xd76aa478)   FF(d, a, b, c, M1, 12, 0xe8c7b756)   FF(c, d, a, b, M2, 17, 0x242070db)   FF(b, c, d, a, M3, 22, 0xc1bdceee)   FF(a, b, c, d, M4, 7, 0xf57c0faf)   FF(d, a, b, c, M5, 12, 0x4787c62a)   FF(c, d, a, b, M6, 17, 0xa8304613)   FF(b, c, d, a, M7, 22, 0xfd469501)   FF(a, b, c, d, M8, 7, 0x698098d8)   FF(d, a, b, c, M9, 12, 0x8b44f7af)   FF(c, d, a, b, M10, 17, 0xffff5bb1)   FF(b, c, d, a, M11, 22, 0x895cd7be)   FF(a, b, c, d, M12, 7, 0x6b901122)   FF(d, a, b, c, M13, 12, 0xfd987193)   FF(c, d, a, b, M14, 17, 0xa679438e)   FF(b, c, d, a, M15, 22, 0x49b40821)   第二轮   GG(a, b, c, d, M1, 5, 0xf61e2562)   GG(d, a, b, c, M6, 9, 0xc040b340)   GG(c, d, a, b, M11, 14, 0x265e5a51)   GG(b, c, d, a, M0, 20, 0xe9b6c7aa)   GG(a, b, c, d, M5, 5, 0xd62f105d)   GG(d, a, b, c, M10, 9, 0x02441453)   GG(c, d, a, b, M15, 14, 0xd8a1e681)   GG(b, c, d, a, M4, 20, 0xe7d3fbc8)   GG(a, b, c, d, M9, 5, 0x21e1cde6)   GG(d, a, b, c, M14, 9, 0xc33707d6)   GG(c, d, a, b, M3, 14, 0xf4d50d87)   GG(b, c, d, a, M8, 20, 0x455a14ed)   GG(a, b, c, d, M13, 5, 0xa9e3e905)   GG(d, a, b, c, M2, 9, 0xfcefa3f8)   GG(c, d, a, b, M7, 14, 0x676f02d9)   GG(b, c, d, a, M12, 20, 0x8d2a4c8a)   第三轮   HH(a, b, c, d, M5, 4, 0xfffa3942)   HH(d, a, b, c, M8, 11, 0x8771f681)   HH(c, d, a, b, M11, 16, 0x6d9d6122)   HH(b, c, d, a, M14, 23, 0xfde5380c)   HH(a, b, c, d, M1, 4, 0xa4beea44)   HH(d, a, b, c, M4, 11, 0x4bdecfa9)   HH(c, d, a, b, M7, 16, 0xf6bb4b60)   HH(b, c, d, a, M10, 23, 0xbebfbc70)   HH(a, b, c, d, M13, 4, 0x289b7ec6)   HH(d, a, b, c, M0, 11, 0xeaa127fa)   HH(c, d, a, b, M3, 16, 0xd4ef3085)   HH(b, c, d, a, M6, 23, 0x04881d05)   HH(a, b, c, d, M9, 4, 0xd9d4d039)   HH(d, a, b, c, M12, 11, 0xe6db99e5)   HH(c, d, a, b, M15, 16, 0x1fa27cf8)   HH(b, c, d, a, M2, 23, 0xc4ac5665)   第四轮   II(a, b, c, d, M0, 6, 0xf4292244)   II(d, a, b, c, M7, 10, 0x432aff97)   II(c, d, a, b, M14, 15, 0xab9423a7)   II(b, c, d, a, M5, 21, 0xfc93a039)   II(a, b, c, d, M12, 6, 0x655b59c3)   II(d, a, b, c, M3, 10, 0x8f0ccc92)   II(c, d, a, b, M10, 15, 0xffeff47d)   II(b, c, d, a, M1, 21, 0x85845dd1)   II(a, b, c, d, M8, 6, 0x6fa87e4f)   II(d, a, b, c, M15, 10, 0xfe2ce6e0)   II(c, d, a, b, M6, 15, 0xa3014314)   II(b, c, d, a, M13, 21, 0x4e0811a1)   II(a, b, c, d, M4, 6, 0xf7537e82)   II(d, a, b, c, M11, 10, 0xbd3af235)   II(c, d, a, b, M2, 15, 0x2ad7d2bb)   II(b, c, d, a, M9, 21, 0xeb86d391)   所有这些完成之后,将A、B、C、D分别加上a、b、c、d。然后用下一分组数据继续运行算法,最后的输出是A、B、C和D的级联。   当你按照我上面所说的方法实现MD5算法以后,你可以用以下几个信息对你做出来的程序作一个简单的测试,看看程序有没有错误。   MD5 ("") = d41d8cd98f00b204e9800998ecf8427e   MD5 ("a") = 0cc175b9c0f1b6a831c399e269772661   MD5 ("abc") = 900150983cd24fb0d6963f7d28e17f72   MD5 ("message digest") = f96b697d7cb7938d525a2f31aaf161d0   MD5 ("abcdefghijklmnopqrstuvwxyz") = c3fcd3d76192e4007dfb496cca67e13b   MD5 ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz") =   f29939a25efabaef3b87e2cbfe641315 VB2010实现   Imports System   Imports System.Security.Cryptography   Imports System.Text   Module Example   ' 哈希输入字符串并返回一个32字符的十六进制字符串哈希。   Function getMd5Hash(ByVal input As String) As String   ' 创建新的一个MD5CryptoServiceProvider对象的实例。   Dim md5Hasher As New MD5CryptoServiceProvider()   ' 输入的字符串转换为字节数组,并计算哈希。   Dim data As Byte() = md5Hasher.ComputeHash(Encoding.Default.GetBytes(input))   ' 创建一个新的StringBuilder收集的字节,并创建一个字符串。   Dim sBuilder As New StringBuilder()   ' 通过每个字节的哈希数据和格式为十六进制字符串的每一个循环。   Dim i As Integer   For i = 0 To data.Length - 1   sBuilder.Append(data(i).ToString("x2"))   Next i   ' 返回十六进制字符串。   Return sBuilder.ToString()   End Function   ' 验证对一个字符串的哈希值。   Function verifyMd5Hash(ByVal input As String, ByVal hash As String) As Boolean   ' 哈希的输入。   Dim hashOfInput As String = getMd5Hash(input)   ' 创建StringComparer1的哈希进行比较。   Dim comparer As StringComparer = StringComparer.OrdinalIgnoreCase   If 0 = comparer.Compare(hashOfInput, hash) Then   Return True   Else   Return False   End If   End Function   Sub Main()   Dim source As String = "Hello World!"   Dim hash As String = getMd5Hash(source)   Console.WriteLine("进行MD5加密的字符串为:" + source + " 加密的结果是:" + hash + ".")   Console.WriteLine("验证哈希...")   If verifyMd5Hash(source, hash) Then   Console.WriteLine("哈希值是相同的。")   Else   Console.WriteLine("哈希值是不相同的。")   End If   End Sub   End Module   ' 此代码示例产生下面的输出:   '   ' 进行MD5加密的字符串为:Hello World! 加密的结果是:ed076287532e86365e841e92bfc50d8c.   ' 验证哈希...   ' 哈希值是相同的。 伪代码实现   //Note: All variables are unsigned 32 bits and wrap modulo 2^32 when calculating   var int[64] r, k //r specifies the per-round shift amounts   r[ 0..15]:= {7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22}   r[16..31]:= {5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20, 5, 9, 14, 20}   r[32..47]:= {4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23}   r[48..63]:= {6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21}   //Use binary integer part of the sines of integers as constants:   for i from 0 to 63   k[i] := floor(abs(sin(i + 1)) × 2^32)   //Initialize variables:   var int h0 := 0x67452301   var int h1 := 0xEFCDAB89   var int h2 := 0x98BADCFE   var int h3 := 0x10325476   //Pre-processing:   append "1" bit to message   append "0" bits until message length in bits ≡ 448 (mod 512)   append bit length of message as 64-bit little-endian integer to message   //Process the message in successive 512-bit chunks:   for each 512-bit chunk of message   break chunk into sixteen 32-bit little-endian words w[i], 0 ≤ i ≤ 15   //Initialize hash value for this chunk:   var int a := h0   var int b := h1   var int c := h2   var int d := h3   //Main loop:   for i from 0 to 63   if 0 ≤ i ≤ 15 then   f := (b and c) or ((not b) and d)   g := i   else if 16 ≤ i ≤ 31   f := (d and b) or ((not d) and c)   g := (5×i + 1) mod 16   else if 32 ≤ i ≤ 47   f := b xor c xor d   g := (3×i + 5) mod 16   else if 48 ≤ i ≤ 63   f := c xor (b or (not d))   g := (7×i) mod 16   temp := d   d := c   c := b   b := ((a + f + k[i] + w[g]) leftrotate r[i]) + b   a := temp   //Add this chunk's hash to result so far:   h0 := h0 + a   h1 := h1 + b   h2 := h2 + c   h3 := h3 + d   var int digest := h0 append h1 append h2 append h3   //(expressed as little-endian) 标准C语言实现   具体的一个MD5实现   /*   * md5 -- compute and check MD5 message digest.   * this version only can calculate the char string.   *   * MD5 (Message-Digest algorithm 5) is a widely used, partially   * insecure cryptographic hash function with a 128-bit hash value.   *   * Author: redraiment   * Date: Aug 27, 2008   * Version: 0.1.6   */   #include   #include   #include   #include   #define SINGLE_ONE_BIT 0x80   #define BLOCK_SIZE 512   #define MOD_SIZE 448   #define APP_SIZE 64   #define BITS 8   // MD5 Chaining Variable   #define A 0x67452301UL   #define B 0xEFCDAB89UL   #define C 0x98BADCFEUL   #define D 0x10325476UL   // Creating own types   #ifdef UINT64   # undef UINT64   #endif   #ifdef UINT32   # undef UINT32   #endif   typedef unsigned long long UINT64;   typedef unsigned long UINT32;   typedef unsigned char UINT8;   typedef struct   {   char * message;   UINT64 length;   }STRING;   const UINT32 X[4][2] = {{0, 1}, {1, 5}, {5, 3}, {0, 7}};   // Constants for MD5 transform routine.   const UINT32 S[4][4] = {   { 7, 12, 17, 22 },   { 5, 9, 14, 20 },   { 4, 11, 16, 23 },   { 6, 10, 15, 21 }   };   // F, G, H and I are basic MD5 functions.   UINT32 F( UINT32 X, UINT32 Y, UINT32 Z )   {   return ( X & Y ) | ( ~X & Z );   }   UINT32 G( UINT32 X, UINT32 Y, UINT32 Z )   {   return ( X & Z ) | ( Y & ~Z );   }   UINT32 H( UINT32 X, UINT32 Y, UINT32 Z )   {   return X ^ Y ^ Z;   }   UINT32 I( UINT32 X, UINT32 Y, UINT32 Z )   {   return Y ^ ( X | ~Z );   }   // rotates x left s bits.   UINT32 rotate_left( UINT32 x, UINT32 s )   {   return ( x << s ) | ( x >> ( 32 - s ) );   }   // Pre-processin   UINT32 count_padding_bits ( UINT32 length )   {   UINT32 div = length * BITS / BLOCK_SIZE;   UINT32 mod = length * BITS % BLOCK_SIZE;   UINT32 c_bits;   if ( mod == 0 )   c_bits = MOD_SIZE;   else   c_bits = ( MOD_SIZE + BLOCK_SIZE - mod ) % BLOCK_SIZE;   return c_bits / BITS;   }   STRING append_padding_bits ( char * argv )   {   UINT32 msg_length = strlen ( argv );   UINT32 bit_length = count_padding_bits ( msg_length );   UINT64 app_length = msg_length * BITS;   STRING string;   string.message = (char *)malloc(msg_length + bit_length + APP_SIZE / BITS);   // Save message   strncpy ( string.message, argv, msg_length );   // Pad out to mod 64.   memset ( string.message + msg_length, 0, bit_length );   string.message [ msg_length ] = SINGLE_ONE_BIT;   // Append length (before padding).   memmove ( string.message + msg_length + bit_length, (char *)&app;_length, sizeof( UINT64 ) );   string.length = msg_length + bit_length + sizeof( UINT64 );   return string;   }   int main ( int argc, char *argv[] )   {   STRING string;   UINT32 w[16];   UINT32 chain[4];   UINT32 state[4];   UINT8 r[16];   UINT32 ( *auxi[ 4 ])( UINT32, UINT32, UINT32 ) = { F, G, H, I };   int roundIdx;   int argIdx;   int sIdx;   int wIdx;   int i;   int j;   if ( argc < 2 )   {   fprintf ( stderr, "usage: %s string ...\n", argv[ 0 ] );   return EXIT_FAILURE;   }   for ( argIdx = 1; argIdx < argc; argIdx++ )   {   string = append_padding_bits ( argv[ argIdx ] );   // MD5 initialization.   chain[0] = A;   chain[1] = B;   chain[2] = C;   chain[3] = D;   for ( j = 0; j < string.length; j += BLOCK_SIZE / BITS)   {   memmove ( (char *)w, string.message + j, BLOCK_SIZE / BITS );   memmove ( state, chain, sizeof(chain) );   for ( roundIdx = 0; roundIdx < 4; roundIdx++ )   {   wIdx = X[ roundIdx ][ 0 ];   sIdx = 0;   for ( i = 0; i < 16; i++ )   {   // FF, GG, HH, and II transformations for rounds 1, 2, 3, and 4.   // Rotation is separate from addition to prevent recomputation.   state[sIdx] = state [ (sIdx + 1) % 4 ] +   rotate_left ( state[sIdx] +   ( *auxi[ roundIdx ] )   ( state[(sIdx+1) % 4], state[(sIdx+2) % 4], state[(sIdx+3) % 4]) +   w[ wIdx ] +   (UINT32)floor( (1UL << 32) * fabs(sin( roundIdx * 16 + i + 1 )) ),   S[ roundIdx ][ i % 4 ]);   sIdx = ( sIdx + 3 ) % 4;   wIdx = ( wIdx + X[ roundIdx ][ 1 ] ) & 0xF;   }   }   chain[ 0 ] += state[ 0 ];   chain[ 1 ] += state[ 1 ];   chain[ 2 ] += state[ 2 ];   chain[ 3 ] += state[ 3 ];   }   memmove ( r + 0, (char *)&chain;[0], sizeof(UINT32) );   memmove ( r + 4, (char *)&chain;[1], sizeof(UINT32) );   memmove ( r + 8, (char *)&chain;[2], sizeof(UINT32) );   memmove ( r + 12, (char *)&chain;[3], sizeof(UINT32) );   for ( i = 0; i < 16; i++ )   printf ( "x", r[i] );   putchar ( '\n' );   free(string.message);    }   return EXIT_SUCCESS;   }   /* 以上程序可以在任意一款支持ANSI C的编译器上编译通过 */   /* 直接复制粘贴,请删除多余的空格,并调整格式,否则可能有编译错误 */   /* 在linux下编译,要添加链接库,命令如:gcc -o md5 md5.c -lm */

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