请用C语言编写程序来实现strncpy strlen strlwr三个功能，不要太复杂的编程，只要能实现就行了！谢谢了

Question

请用C语言编写程序来实现strncpy strlen strlwr三个功能，不要太复杂的编程，只要能实现就行了！谢谢了。。。很急的喔

Answer 1

#include <stdio.h>
char* mystrncpy(char* strdst, const char* strsrc, int count)
{
    char *ret = strdst;
    while (count>0 && *strsrc)
    {
        *strdst = *strsrc;
        strdst++;
        strsrc++;
        count--;
    }
    *strdst = 0;
    return ret;
}
unsigned int mystrlen(const char* str)
{
    unsigned int ret = 0;
    while (*str)
    {
        ret++;
        str++;
    }
    return ret;
}
char* mystrlwr(char* str)
{
    char* ret = str;
    while(*str)
    {
        if (*str >= 65 && *str <= 90)
            *str += 32;
        str++;
    }
    return ret;
}
void main()
{
    char strTest[] = "1234567890ABCDEFGabcdefg";
    char strResult[100];
    ;
    printf("Test mystrncpy for 15 characters: %s\n", mystrncpy(strResult, strTest, 15));
    printf("Test mystrncpy for 90 characters: %s\n", mystrncpy(strResult, strTest, 90));
    printf("Test mystrlen: %d\n", mystrlen(strTest));
    printf("Test mystrlwr: %s\n", mystrlwr(strTest));
}

Answer 2

这三个函数够本征了……实在要写，得用赋值语句了……追问

我想问的是：在编程中体现它们的功能，三个分开写！谢谢了