自定义写string中的一些库函数
(1)strcat()——mystrcat()
void mystrcat(char *s1,char *s2)
{
int i = 0,j = 0;
while(s1[i] != '\0')
{
i++;
}
while(s2[j] !='\0')
{
s1[i] = s2[j];
i++;
j++;
}
s1[i] = '\0';
}
(2)strcpy()——mystrcpy()
void mystrcpy(char s1[],char s2[])
{
int i = 0;
while (s2[i] != '\0')
{
s1[i] = s2[i];
i++;
}
s1[i] = '\0';
}
(3)strcmp()——mystrcmp()
int mystrcmp(char *s1,char *s2)
{
while(*s1 == *s2)
{
if(*s1 == '\0')
{
return 0;
}
s1++;
s2++;
}
return *s1 - *s2; //不相同则返回字符差值
(4)strlen()——mystrlen()
int mystrlen(char *s)
{
//记录串长度,不记录\0
int i = 0;
while(*s != '\0')
{
s++;
i++;
}
return i;
}
(5)strlwr()——mystrlwr()
void mystrlwr(char *s)
{
int i = 0;
while (s[i] != '\0')
{
if(s[i] >= 'A' && s[i] <= 'Z')
{
s[i] += 'a' - 'A';
}
i++;
}
}
(6)strupr()——mystrupr()
void mystrupr(char *s)
{
int i = 0;
while (s[i] != '\0')
{
if(s[i] >= 'a' && s[i] <= 'z')
{
s[i] -= 'a' - 'A';
}
i++;
}
}