//模拟实现库函数strcat函数#include 
     
      #include 
      
       #include 
       
        char * my_strcat(char *dst, const char *src){	char *start = dst;	int len_dst = strlen(dst);	dst+=len_dst;	while (*dst++ = *src++)	{		;	}	return start;}int main(){	char a[20] = "hello ";	char *p = "world!";	printf("%s\n", my_strcat(a, p));	return 0;}