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

#include <stdio.h>梁拦

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)

    {

    橡旁胡    ret++

      启闷  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))

}

/***

*char *strcat(dst, src) - concatenate (append) one string to another

*

*Purpose:

* Concatenates src onto the end of dest. Assumes enough

* space in dest.

*

*Entry:

* char *dst - string to which "src"和激 is to be appended

* const char *src - string to be appended to the end of "dst"

*

*Exit:

* The address of "dst"

*

*Exceptions:

*

*******************************************************************************/

char * __cdecl strcat (

char * dst,

const char * src

)

{

char * cp = dst

while( *cp )

cp++ /* find end of dst */

while( *cp++ = *src++ ) /铅亩* Copy src to end of dst */

return( dst ) /* return dst */

}

/***

*char *strcpy(dst, src) - copy one string over another

*

*Purpose:

* Copies the string src into the spot specified by

* destassumes enough room.

*

*Entry:

* char * dst - string over which "src" is to be copied

* const char * src - string to be copied over "dst"

*

*Exit:

* The address of "dst"

*

*Exceptions:

*******************************************************************************/

char * __cdecl strcpy(char * dst, const char * src)

{

char * cp = dst

while( *cp++ = *src++ )

/* Copy src over dst */

return( dst )

}

//以上是微软的实现，更多的到VC++安装盘下CRT目槐棚森录找吧

#include<stdio.h>

#include<string>

void strlwr_trans(char *str){

 int i=0

 while(str[i]!='\0'){

  if(str[i]>='A'&&str[i]<='Z')

   printf("宏扰%c"哗绝旅,str[i]+32)

  else printf("%c",str[i])

  i++

 }

}

void strupr_trans(char *str){

 int i=0

 while(str[i]!='\0'){

  if(str[i]>='a'&&str[i]<='z')

   printf("%c",str[i]-32)

  else 乱凳printf("%c",str[i])

  i++

 }

}

int main(){

 char str[100]

 scanf("%s",str)

 strupr_trans(str)

 printf("\n")

 strlwr_trans(str)

 return 0

}

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