模拟实现库函数strcat、strcmp

strcat：字符串追加

模拟实现strcat

#include <stdio.h>
#include <assert.h>
char* my_strcat(char* dest, const char* src)
{
	assert(dest);
	assert(src);
	char* ret = dest;//记录起始地址
    //1. 找到目标空间的末尾，即'\0'
	while (*dest != '\0')
	{
		dest++;
	}
	//2. 拷贝字符串
	while (*dest++ = *src++)
	{
		;
	}
	return ret;
}
int main()
{
	char arr1[20] = "hello ";
	my_strcat(arr1,"world");
	printf("%s\n", arr1);
	return 0;
}

strcmp：比较两个字符串是否相等

模拟实现strcmp

#include <stdio.h>
#include <assert.h>
int my_strcmp(const char* str1,const char* str2)
{
	assert(str1 && str2);
	while (*str1 == *str2)
	{
		if (*str1 == '\0')
			return 0;//相等
		str1++;
		str2++;
	}
	if (*str1 > *str2)
		return 1;
	else
		return -1;
}
int main()
{
	char arr1[] = "abc";
	char arr2[] = "ac";
	int ret = my_strcmp(arr1, arr2);
	if (ret < 0)
	{
		printf("<\n");
	}
	else if (ret == 0)
	{
		printf("==\n");
	}
	else
	{
		printf(">\n");
	}
	return 0;
}