面试之自定义字符串操作

面试之自定义字符串操作

1. strcpy

   #include <assert.h>
   char *strcpy(char *dest, const char *src)
   {
   	assert( (dest != NULL) && (src != NULL);
      	char *address = dest;
       while((*dest++ = *src++) != '');
       return address;
   }
    
   

2. strcmp

   #include <assert.h>
   
   
   int strcmp(const char *str1, const char *str2)
   {
       assert((str1 != NULL) && (str2 != NULL));
       for (; (*str1) && (*str2) && (*str1 == *str2);++ str1,++ str2);
       return (*str1 - *str2);
   }
   

3. strcat

   char *m_strcat(char *dest, const char *src)
   {
       assert((dest != NULL) && (src != NULL));
       char *add = dest;
       while (*dest != '')
           ++dest;
       while (*dest++ = *src++);
       return add;
   }
   

4. strlen

   unsigned int m_strlen(const char *str)
   {
       assert(str != NULL);
       int len = 0;
       while (*str != '')
       {
           ++str;
           ++len;
       }
       return len;
   }