模拟实现字符串操作函数

1.模拟实现strcpy

//模拟实现字符串拷贝函数strcpy
#include <stdio.h>
#include <stdlib.h>

char* my_strcpy(char* dest,const char* src)
{
char* ch = dest;
while(*dest++ = *src++)//*(p++)解引用操作符、后置++，结合方向自右向左
;
return ch;
}

int main()
{
int i = 0;
char arr[20];
char* ret = my_strcpy(arr,"hello world");
printf("%s\n",ret);

system("pause");
return 0;
}

运行结果：

2.模拟实现strcmp

//模拟实现字符串比较函数strcmp
#include <stdio.h>
#include <stdlib.h>

int mystrcmp(char *str1, char *str2)
{
while(*str1 || *str2)
{
if(*str1 == *str2)
{
str1++;
str2++;
}
else
{
return -1;
}
}
if(*str1 == *str2)
{
return 1;
}
else
{
return -1;
}
}

int main()
{
char arr1[] = "hello";
char arr2[] = "hello world";
int ret = mystrcmp(arr1, arr2);
if(ret == 1)
{
printf("这两个字符串相同\n");
}
else
{
printf("这两个字符串不同\n");
}

system("pause");
return 0;
}

运行结果：

3.模拟实现strcat

//模拟实现字符串粘贴函数strcat
#include <stdio.h>
#include <stdlib.h>

char* mystrcat(char *str1, char *str2)
{
char *p1 = str1;
char *p2 = str2;
while(*p1)
{ 
p1++;
}
while(*p2)
{
*p1 = *p2;
p1++;
p2++;
}
*p1 = '\0';
return str1;
}

int main()
{
char arr1[100] = "hello ";
char arr2[] = "world";

char *arr = mystrcat(arr1, arr2);
    printf("%s\n",arr);

system("pause");
return 0;
}

运行结果：