C++字符串内部查找函数

char* strchr( const char* str, int chr );

在str中查找第一次出现的chr，没找到则返回0

char* strrchr( const char* str, int chr );

在str中查找最后一次出现的chr，没找到则返回0

char* strstr( const char* str, const char* substr );

在str中查找第一次出现的substr，没找到则返回0

size_t strspn( const char* str, const char* chrset );

在str中查找 只包含在chrset中的字符 的最开始的最长字符数目

strspn( "cabbage", "abc" ) == 5;

strspn( "cabbage", "dc" ) == 1;

strspn( "cabbage", "d" ) == 0;

strspn( str, "abceg" ) == 7;

char* strspnp( const char* str, const char* chrset );

和strspn功能一样，只是返回指针

const char* str = "cabbage"

strspnp( str, "abc" ) == str+5;

strspnp( str, "dc" ) == str+1;

strspnp( str, "d" ) == str+0;

strspnp( str, "abceg" ) == 0; // 和strspn不一样

size_t strcspn( const char* str, const char* chrset );

在str中查找第一次出现在chrset中的字符位置，没找到则返回str结尾的'/0'的位置

strcspn( "xyzbxz", "abc" ) = 3

strcspn( "xyzbxz", "xyz" ) = 0

strcspn( "xyzbxz", "no match" ) = 6

strcspn( "xyzbxz", "" ) = 6

strcspn( "", "abc" ) = 0

strcspn( "", "" ) = 0

char* strpbrk( const char* str, const char* chrset );

和strcspn功能一样，只是返回指针

strpbrk( "xyzbxz", "abc" ) = "xyzbxz"+3

strpbrk( "xyzbxz", "xyz" ) = "xyzbxz"+0

strpbrk( "xyzbxz", "no match" ) = 0 // 和strcspn不一样

strpbrk( "xyzbxz", "" ) = 0 // 和strcspn不一样

strpbrk( "", "abc" ) = 0 // 和strcspn不一样

strpbrk( "", "" ) = 0 // 和strcspn不一样

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假如想将 "123@456@789" 分割成 "123" "456" "789" 当用 strchr

假如想将 "123@#456@#789" 分割成 "123" "456" "789" 当用 strstr

假如想将 "123@456#789@#0" 分割成 "123" "456" "789" "" "0" 当用 strcspn

假如想将 "123@456#789@#0" 分割成 "123" "456" "789" "0" 当用 strcspn/strspn

代码如下：（未曾测试过）

#include <stdio.h>

#include <string.h>

#include <assert.h>

void split001( const char* str, const char chr )

{

const char* p1 = str;

for( const char* p2; (p2=strchr(p1,chr))!=0; p1=p2+1 )

{

printf( "/"%.*s/"/n", p2-p1, p1 );

}

printf( "/"%s/"/n", p1 );

}

void split002( const char* str, const char* substr )

{

assert( *substr );

const size_t substrlen = strlen(substr);

const char* p1 = str;

for( const char* p2; (p2=strstr(p1,substr))!=0; p1=p2+substrlen )

{

printf( "/"%.*s/"/n", p2-p1, p1 );

}

printf( "/"%s/"/n", p1 );

}

void split003( const char* str, const char* substr )

{

assert( *substr );

const char* p1 = str;

for( const char* p2; p2=p1+strcspn(p1,substr), *p2; p1=p2+1 )

{

printf( "/"%.*s/"/n", p2-p1, p1 );

}

printf( "/"%s/"/n", p1 );

}

void split004( const char* str, const char* substr )

{

assert( *substr );

const char* p1 = str;

for( const char* p2; p2=p1+strcspn(p1,substr), *p2; p1=p2+strspn(p2,substr) )

{

printf( "/"%.*s/"/n", p2-p1, p1 );

}

printf( "/"%s/"/n", p1 );

}

int main( void )

{

split001( "123@456@789", '@' );

printf( "---/n" );

split002( "123@#456@#789", "@#" );

printf( "---/n" );

split003( "123@456#789@#0", "@#" );

printf( "---/n" );

split004( "123@456#789@#0", "@#" );

printf( "---/n" );

return 0;

}