1. 封装函数实现strlen功能

#include <stdio.h>size_t MyStrlen(const char *pstr)
{size_t cnt = 0;while (*pstr++ != '\0'){++cnt;}return cnt;
}int main(void)
{char str[256] = {0};size_t len = 0;gets(str);len = MyStrlen(str);printf("数组长度为：%ld\n", len);return 0;
}

2. 封装函数实现strcpy功能

#include <stdio.h>char *MyStrcpy(char *str_1, const char *str_2)
{char *str = str_1; while (*str_2 != '\0'){*str_1 = *str_2;str_1++;str_2++;}*str_1 = '\0';return str;
}int main(void)
{char str_1[30] = {0};char str_2[30] = {0};gets(str_2);MyStrcpy(str_1, str_2);puts(str_1);return 0;
}

3. 封装函数实现strcat功能

#include <stdio.h>char *MyStrcat(char *str_1, const char *str_2)
{char *str = str_1;while (*str_1++ != '\0');--str_1;while (*str_2 != '\0'){*str_1++ = *str_2++;}*str_1= '\0';return str;
}int main(void)
{char str_1[30] = {"hello"};char str_2[30] = {"world"};MyStrcat(str_1, str_2);puts(str_1);return 0;
}

4. 封装函数实现strcmp功能

#include <stdio.h>int MyStrcmp(char *str_1, char *str_2)
{while (*str_1 == *str_2 && *str_1 != '\0'){str_1++;str_2++;}return *str_1 - *str_2;
}int main(void)
{char str_1[30] = {0};char str_2[30] = {0};int num = 0;gets(str_1);gets(str_2);num = MyStrcmp(str_1, str_2);printf("num = %d\n", num);return 0;
}