ios-c_day11___ string

2015.2.2

#include <stdio.h>

#include <ctype.h>

Functions for character manipulation

int isalnum (int);

int isalpha (int);

int isdigit (int);

int isgraph (int);

int islower (int);

int ispunct (int);

int isspace (int);//Determines whether it is a space

int isupper (int);

int isxdigit (int);

int tolower (int);

int toupper (int);

int digittoint (int);

int ishexnumber (int);

int isnumber (int);

int main (int argc, const char * argv[]) {

//

printf ("isalnum =%d\n", Isalnum (' a '));//Determine if it is a numeric character or an English letter

printf ("Isalpha =%d\n", Isalpha (' * '));//Determine if it is an English letter

printf ("IsDigit =%d\n", IsDigit (' & '));//Determine if the numeric character

printf ("Isgraph =%d\n", isgraph (' \ n '));//Determine if it is a visible character

printf ("Islower =%d\n", islower (' * '));//Determines whether it is a lowercase letter

printf ("ispunct =%d\n", ispunct (';')); /Judging whether it is a punctuation mark

printf ("Isupper =%d\n", Isupper (' A '));//Determine if uppercase

printf ("Isxdigit =%d\n", Isxdigit (' a '));//Determine if it is a hexadecimal character

printf ("ToLower =%c\n", ToLower (' A '));//Convert to lowercase

printf ("ToUpper =%c\n", ToUpper (' a '));//Convert to uppercase

printf ("Digittoint =%d\n", Digittoint (' F '));//convert hexadecimal characters to integer data

printf ("Ishexnumber =%d\n", Ishexnumber (' 9 '));//Same as Isxdigit function

printf ("Isnumber =%d\n", Isnumber (' 9 '));//Same as isdigit function

return 0;

//}

String

"Hello World"

1. Double quotation marks contain

2. Each element in a string consumes one byte of memory space

3. A hidden character at the end of the string ' \ s '

//

The print string corresponds to the first address of the string to be printed with%s

storing strings in a character array, or requesting memory

Gets ()//Enter a string

Puts ()//Output a string

int main (int argc,const char *argv[])

//{

Char str[12]= "Hello World";

printf ("%s\n", str);//%s print string encountered ' \ n ' End

//

Char str2[100];

Get (STR2);//meet ' \ n ' End

Puts (STR2);

//

return 0;

//}

Char str1[100]= "Hello World"

Char *str2= "Hello World";

int main (int argc,const char *argv[])

//{

Char str1[100]= "Hello World";

Char *str2= "Hello World";//str2 points to the constant area, the contents of the constant area are read-only and cannot be modified

//

*STR2 = ' a ';

Str1[0]= ' a ';

printf ("%s\n", str1);

return 0;

//}

String length (usually referred to as string valid length)

"Hello World"

Valid length does not contain the ' + ' at the end of the string

sizeof strlen

Difference:

1.sizeof is an operator, strlen is a function

2.sizeof variables or constants occupy memory space size, strlen to find the number of valid characters, the operand is a string

The 3.sizeof operator is the concept of a compilation hierarchy, and the strlen function is the concept of a running hierarchy

#include <string.h>

size_t <==> unsigned long

size_t My_strlen (const char *SRC)

//{

if (!SRC) {

return 0;

//    }

int len=0;

while (*src! = ')} {

len++;

src++;

////    }

for (; *src;) {

len++;

src++;

//    }

return Len;

//}

//

int main (int argc, char *argv[])

//{

Char str[100]= "Qian Feng";

char *pstr = str;

printf ("%ld\n", sizeof (str));

//

printf ("%ld\n", My_strlen (str));

//

printf ("%ld\n", sizeof (PSTR));//The amount of memory space occupied by the pointer variable

printf ("%ld\n", strlen (PSTR));

//

return 0;

//}

string comparison function

int strcmp (const char *, const char *);

int strncmp (const char *, const char *, size_t);

size_t: Limit the maximum number of comparison characters

return value greater than 0 str1 > str2

equals 0 str1 = = str2

Less than 0 str1 < str2

int my_strcmp (const char *STR1, const char *STR2)

//{

while (*str1==*str2 && *str1 && *str2) {

str1++;

str2++;

//    }

return *STR1-*STR2;

//}

//

int main (int argc,const char *argv[])

//{

Char *str1 = "ABCDEFGH";

char *STR2 = "abc";

//

int ret = MY_STRCMP (str1, str2);

printf ("ret =%d\n", ret);

//

ret = strncmp (str1, str2, 7);

printf ("ret =%d\n", ret);

//

return 0;

//}

String Lookup

Strchr

Char *STRCHR (const char *, int);

Find the first occurrence of a character in the original string from left to right, no return null found

Strrchr

Char *STRRCHR (const char *, int);

Reverse lookup character, find the first occurrence of the position returned, cannot find return null

Char *my_strchr (const char *SRC, char ch)

{

while (*SRC) {

if (*src==ch) {

Return (char *) src;

}

src++;

}

return NULL;

}

Char *my_strrchr (const char *SRC, char ch)

{

size_t len = strlen (src);

for (long I=len; i>=0; i--) {

if (* (src+i) ==ch) {

Return (char *) (src+i);

}

}

return NULL;

}

int main (int argc,const char *argv[])

//{

char *str = "Hello World";

//

printf ("%s\n", MY_STRCHR (str, ' o '));

//

printf ("%s\n", MY_STRRCHR (str, ' o '));

//

//

return 0;

//}

String copy

Char *strcpy (char *dest, const char *src);

The memory that dest and SRC point to cannot have overlapping parts

Dest space enough to accommodate the SRC string

Char *strncpy (char *dest, const char *SRC, size_t len);

Len limits the number of characters that can be copied to the Dest buffer

len = sizeof (dest)-1

Char *my_strcpy (char *dest, const char *SRC)

{

char *temp = dest;

while (*SRC) {

*temp = *SRC;

temp++;

src++;

}

*temp = ' + ';

return dest;

}

Char *my_strncpy (char *dest, const char *SRC, size_t len)

{

size_t i=0;

char *temp = dest;

while (*src && I<len) {

*temp = *SRC;

temp++;

src++;

i++;

}

if (I<len) {

*temp = ' + ';

}

return dest;

}

int main (int argc, const char *argv[])

//{

Char dest[100]= "Qianfengabcdef";

Char *src = "HelloWorld";

printf ("%s\n", my_strcpy (dest, SRC));

printf ("%s\n", dest);

printf ("%s\n", strcpy (dest, &dest[4])),//strcpy-manipulated string memory does not overlap

//

printf ("%s\n", my_strncpy (dest, SRC, 100-1));

return 0;

//}

string concatenation

Char *strcat (char *dest, const char *src);

1. Determine that the remaining memory space of the dest is sufficient to accommodate the SRC string

Char *strncat (char *dest, const char *SRC, size_t len);

len = sizeof (dest)-strlen (dest)-1;

Len allows a maximum number of characters to be stitched into the dest buffer, and after stitching, add ' + ' at the end of the new string;

Char *my_strcat (char *dest, const char *SRC)

{

size_t len = strlen (dest);

int i=0;

while (*SRC) {

* (dest+len+i) = *SRC;

src++;

i++;

}

* (dest+len+i) = ' + ';

return dest;

}

Char *my_strncat (char *dest, const char *SRC, size_t len)

{

size_t i=0;

size_t size = strlen (dest);

char *temp = dest+size;

while (*src && I<len) {

*temp = *SRC;

temp++;

src++;

i++;

}

*temp = ' + ';

return dest;

}

int main (int argc,const char *argv[])

//{

Char dest[21]= "Hello World";

dest[20]= ' A ';

dest[16]= ' W ';

Char *src = "Qian Feng";

printf ("%s\n", My_strcat (dest, SRC));

//

printf ("%s\n", My_strncat (dest, src,4));

//

return 0;

//}

String segmentation

Strtok

Char *strtok (char *src, const char *demi);

int main (int argc,const char *argv[])

//{

Char src[100]= "Root:qian;:feng,:jiao;yu";

Char *ps = strtok (src, ";,:");//The bottom layer divides the delimiter into '

printf ("%p%s\n", ps,ps);//delimiters must be enclosed in double quotes, even if there is only one character

printf ("%p%s\n", SRC,SRC);

//

PS = Strtok (NULL, ":;,");

printf ("%s\n", PS);

//

PS = Strtok (NULL, ":;,");

printf ("%s\n", PS);

//

PS = Strtok (NULL, ":;,");

printf ("%s\n", PS);

//

PS = Strtok (NULL, ":;,");

printf ("%s\n", PS);

//

return 0;

//}

int main (int argc,const char *argv[])

//{

Char str[100]= "Root:qian;:feng,:jiao;yu";

//

char *pstr = str;

while ((Pstr = Strtok (Pstr, ":;,"))) {

printf ("%s\n", pstr);

Pstr = NULL;

//    }

//

return 0;

//}

Find a child string

Strstr

Char *strstr (const char *SRC, const char *substr);

Returns the address of the first occurrence of a substring in the original string, without which the substring in the original string returns null

Char *my_strstr (const char *SRC, const char *SUBSTR)

{

Char *sub = (char *) substr;

while (*SRC) {

Char *temp = (char *) src;

while (*src++ = = *substr++) {

if (*substr = = ' + ') {

return temp;

}

}

src = temp+1;

substr = Sub;

}

return NULL;

}

int main (int argc,const char *argv[])

//{

Char src[100]= "Hello Wwworldqian World Feng";

printf ("%s\n", My_strstr (SRC, "World"));

//

return 0;

//}

"Qianarefengarejiaoareyu"

"Is"

Qian Feng Jiao Yu

int main (int argc,const char *argv[])

//{

Char str[100]= "Qianarefengarejiaoareyu";

Char *p,*q;

p = q = str;

int len = strlen ("is");

while (P = strstr (P, "is")) {

*p = ' + ';

printf ("%s\n", Q);

p+= Len;

Q = p;

//    }

if (*q) {

printf ("%s\n", Q);

//    }

return 0;

//}

SSCANF sprintf

int sscanf (const char *, const char *, ...)

int sprintf (char *, const char *, ...);

int main (int argc,const char *argv[])

{

Char str[100]= "$GPGGA, 4250.5589,s,14718.5084,e";

Char header[100]={};

Char Ch1, CH2;

float South;

float East;

SSCANF (str, "%6s,%f,%c,%f,%c", HEADER,&SOUTH,&CH1,&EAST,&CH2);

printf ("%.2f%.2f\n", South, east);

Char buf[100];

sprintf (buf, "%d***%d", 12,45);

printf ("%s\n", buf);

return 0;

}

ios-c_day11___ string