Shulou(Shulou.com)06/02 Report--

This article mainly explains the "how to copy C language string.h header file test string function", the content of the article is simple and clear, easy to learn and understand, the following please follow the editor's ideas slowly in depth, together to study and learn "how to copy C language string.h header file test string function" bar!

C language string.h header file string checking function imitation

Required header files: stdio.h, stdlib.h, string.h

Strlen string length int strlen_my (const char* src_str) {if (NULL = = src_str) {return-1;} const char* p = src_str; while (* p! ='\ 0') {paired strings;} return p-& (src_str [0]) } / / Recursive int strlen_my2 (const char* src_str) {if (src_str = NULL) return-1; if (* src_str) {return strlen_my2 (src_str + 1) + 1;} else {return 0;}} int main () {const char* p = "hello" Printf ("% d\ n", strlen_my (p)); return 0;} strcmp / strncmp string comparison int strcmp_my (const char* str_a, const char* str_b) {while ((* str_a! ='\ 0' | | * str_b! ='\ 0') & & * str_a = = * str_b) {str_a++; str_b++ } return * str_a-* str_b > 0? 1: (* str_a-* str_b

< 0 ? -1 : 0);}int strcmp_my2(const char* str_a, const char* str_b){ int sub = 0; while ((sub = *str_a - *str_b) == 0 && *str_a++ && *str_b++); //先赋值，指针再++ return sub >

0? 1: (sub

< 0 ? -1 : 0);} int strncmp_my(const char* str_a, const char* str_b, size_t front_len){ while (--front_len && *str_a != '\0' && *str_b != '\0' && *str_a == *str_b) { str_a++; str_b++; } return *str_a - *str_b >

0? 1: (* str_a-* str_b

< 0 ? -1 : 0);} int main(){ const char* p = "hella"; const char* q = "hell"; printf("%d \n", strncmp_my(p, q, 4)); return 0;}strchr / strrchr 字符串中查找字符ch第一个出现的字符ch//strchr 返回字符串中第一个出现的字符chchar* strchr_my(const char* src_str, char ch){ if (src_str == NULL) { return NULL; } while (*src_str != '\0' && *src_str != ch) { src_str++; } return *src_str == '\0' ? NULL : src_str;} int main(){ const char* p = "hello"; p = strchr_my(p, 'e'); if (p == NULL) return 0; printf("%c\n", *p);}最后一个出现的字符ch//strrchr查找字符串中最后一个出现的字母chchar* strrchr_my(const char* src_str, char ch){ if (NULL == src_str) return NULL; const char* p = src_str + strlen(src_str) - 1; while ((p - src_str) >

= 0 & & * p! = ch) {if (p-src_str = =-1) {return NULL;} return p;} int main () {const char* p = "hello"; / / p = strchr_my (p,'q'); p = strrchr_my (p,'l') If (p = = NULL) return 0; printf ("% c\ n", * p);} strstr string matching: find des_str in src_str and return the starting position of the match, but not NULL (BF algorithm) char* strstr_my (const char* src_str, const char* des_str) {if (NULL = = src_str | | NULL = = des_str) {return NULL } int len_src = strlen (src_str); int len_des = strlen (des_str); int I = 0; / / src_str int j = 0 } int main () {const char* p = "hello"; const char* Q = "llo"; const char* rt = strstr_my (p, Q); if (rt! = NULL) {printf ("% s\ n", rt); return 0;} return 0 } strcpy / strncpy string copy char* strcpy_my (char* des_str, const char* src_str) {if (des_str = = NULL | | src_str = = NULL) return NULL; char* p = des_str; while (* src_str! ='\ 0') {* paired + = * src_str++;} * p ='\ 0' Return des_str;} char* strncpy_my (char* des_str, const char* src_str, size_t len) {if (des_str = = NULL | | src_str = = NULL | | len

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.