【c语言strcpy、strcat、strlen函数实现】

c语言strcpy、strcat、strlen函数实现

#include <stdio.h>


//实现strlen函数
int Mystrlen(char *str)
{
    
    
	int len = 0;
	while(*str != '\0')
	{
    
    
		str++;
		len++;	
	}	
	return len;
}

//实现strcpy函数
void Mystrcpy(char *des,const char *src)
{
    
    
	if(NULL == des)
	{
    
    
		return ;
	}	
	while(*src != '\0')
	{
    
    
		*des++ = *src++;
	}
	*des = '\0';	
} 

//实现strcat
char *Mystrcat(char *des,const char *src)
{
    
    
	char *temp = NULL;
	temp = des;  //保存目的字符串首地址
	while(*des++);
	des--;  //指向结束字符串
	while(*des++ = *src++); //进行循环赋值
	*des = '\0';
	return temp; 
} 
 
 
int main(void)
{
    
    
	int result = 0;
	char *str = "hello";
	char *str2 ="world"; 
	result = Mystrlen(str);
	printf("result = %d\n",result);

	//测试二
	char des[24]= {
    
    0};
	Mystrcpy(des,str);
	printf("des = %s\n",des);
	
	//测试三 
	char *res = (char *)malloc(24);
	res =Mystrcat(Mystrcat(res,str),str2);
	printf("str = %s\n",res);
	return 0; 	
}