模拟实现不受限制的字符串函数--C语言版

//模拟实现strlen
// 计算器版本
//#include<stdio.h>
//#include<assert.h>
//int my_strlen(const char *str)
//{
//	assert(str);
//	int count = 0;
//	while (*str++ != 0)
//	{
//		count++;
//	}
//	return count;
//}
//
//int main()
//{
//	char arr[] = {"abcdef"};
//	int ret = my_strlen(arr);
//	printf("%d", ret);
//	return 0;
//}

#include<stdio.h>
#include<string.h>
void mine_strcpy(char* dest, char* sou)
{
    while (*dest++ = *sou++)//当sou将\0传给dest时,while里面的值是0,自动结束了循环---既copy了\0
                              //又使循环停止
    {
        ;
    }
}
int main()
{
    char arr1[] = "aaaaaaaaaaaaaa";
    char arr2[] = "hello";
    mine_strcpy(arr1, arr2);
    printf("%s\n", arr1);
    return 0;
}

#include<stdio.h>
#include<string.h>
#include<assert.h>
char* my_strcat(char* dest, const char* src)
{
    assert(dest &amp;&amp; src);
    char* ret = dest;
   //1.找到目标字符串的\0
    while (*dest)
    {
        dest++;
    }
   //2.接着追加过去(包括\0)（就是strcpy的思路）
    while (*dest++ = *src++)
    {
        ;
    }
    return ret;
}
int main()
{
    char arr1[50] = {"stay foolish,"};
    char arr2[20] = {"stay hungry"};
    //my_strcat(arr1, arr2);
    printf("%s", my_strcat(arr1, arr2));//链式访问
    return 0;
}

//模拟实现strcmp
#include<stdio.h>
#include<assert.h>
int my_strcmp(const char* p,const char* q)
{
    assert(p &amp;&amp; q);
    while (*p == *q)
    {
        if (*p == '\0')//*q也为'\0'
        {
            return 0;
        }
        p++;
        q++;
    }
  //if (*p > *q)
    //	return 1;
    //else
        //return -1;
    return  *p - *q;
}
int main()
{
    char p[] = "abcd";
    char q[] = "abe";
    int ret = my_strcmp(p, q);
    if (ret > 0)
        printf("p>q\n");
    else if (ret < 0)
        printf("p<q\n");
    else
        printf("p==q\n");
    return 0;
}