指针-字符处理-字符旋转

#include <cstdio>
#include <cstring>

void rotate(char *start, char *end)
{
    while(start != NULL && end !=NULL && start<end)
    {
        char temp=*start;
        *start=*end;
        *end=temp;
        start++;
        end--;
    }

}

void left_right_rotate(char *p,int m)
{
    if(p==NULL)
        return ;
    int len=strlen(p);
    char *xfirst,*xend;
    char *yfirst,*yend;
    if(m>0)
    {
        m =m%len;

        xfirst=p;
        xend=p+m-1;
        yfirst=p+m;
        yend=p+len-1;
        rotate(xfirst,xend);
        rotate(yfirst,yend);
        rotate(p,p+len-1);
    }
    else if (m==0) return;
    else
    {
        m=(-1)*m;
        m= m%len;
        m=len-m;
        xfirst=p;
        xend=p+m-1;
        yfirst=p+m;
        yend=p+len-1;
        rotate(xfirst,xend);
        rotate(yfirst,yend);
        rotate(p,p+len-1);
    }
}

int main(void)
{
    char str[]="abcdefghij";
    printf("%s\n",str);
    left_right_rotate(str,-3);
    printf("%s\n",str);
    return 0;
}