模拟实现字符串函数strcat和strcmp

my_strcat函数实现

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <assert.h>
#include <string.h>

char* my_strcat(char* dest, const char* src)
{
	assert(dest && src);
	char* ret = dest;
	//找目标串的'\0'
	while (*dest != '\0')
	{
		dest++;
	}
	/*while (*src != '\0')
	{
		*dest = *src;
		dest++;
		src++;
	}*/
	//另一种写法
	while (*dest++ = *src++)
	{
		;
	}
	return ret;
}
int main()
{
	char arr1[20] = "abc";
	char arr2[] = "defgh";
	char* pc = my_strcat(arr1, arr2);
	printf("%s", pc);
	return 0;
}

my_strcmp函数实现

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <assert.h>
#include <string.h>

int my_strcmp(const char* str1, const char* str2)
{
	assert(str1 && str2);
	while (*str1 == *str2)
	{
		if (*str1 == '\0')
		{
			return 0;
		}
		str1++;
		str2++;
	}
	/*if (*str1 > *str2)
	{
		return 1;
	}
	else
	{
		return -1;
	}*/
	//另一种写法
	return (*str1 - *str2);
}
int main()
{
	char arr1[] = "abcdf";
	char arr2[] = "abcde";
	int ret = my_strcmp(arr1, arr2);
	printf("%d", ret);
	return 0;
}