将字符串中的大写字母变成小写字母

/*字符串中大写字母变成小写，其余字符不变*/#include <stdio.h>
#include <string.h>char* mystrlwr(char *s)
{char *scopy = s;while (*s) {if (*s >= 'A' && *s <= 'Z') {*s = *s + 'a' - 'A';}s++;}return scopy;
}char *mysed_strlwr(char *s)
{char *scopy = s;while (*s) {if (isupper(*s)) {*s = tolower(*s);}s++;}return scopy;
}int main(void)
{char s[] = "HeLLowoRLD";

        printf("%s\n", mystrlwr(s)); printf("%s\n", mysed_strlwr(s));return 0;
}