(1)暴力旋转O(N^2)
#include<stdio.h>
#include<string.h>
void rotate_str(char *str,int k)
{
int len = strlen(str);
while(k%len--)
{
char ch = str[0];
char *p1 =str;
char *p2 = str+1;
while(*p2)
{
*p1 = *p2;
p2++;
p1++;
}
*p1 = ch;
}
}
int main()
{
char str[] = "ABCDEF";
int k = 12;
printf("%s\n",str);
rotate_str(str,k);
printf("%s\n",str);
return 0;
}
(2)要左旋k个字符,先把前k个字符逆置,再把剩余的字符逆置,最后整体逆置
#include<stdio.h>
#include<string.h>
//先逆置k个字符,再把剩余字符逆置,最后整体逆置
void Swap(char *p1,char *p2)
{
char tmp = *p1;
*p1 = *p2;
*p2 = tmp;
}
void rotate(char *str,int k)
{
int len = strlen(str);
char *p1 = str;
char *p2 =str + k%len-1;
char *p3 = p2+1;
char *p4 = str+len-1;
while(p1<=p2)
{
Swap(p1,p2);
p1++;
p2--;
}
while(p3<=p4)
{
Swap(p3,p4);
p3++;
p4--;
}
p1 = str;
p4 = str+len-1;
while(p1<=p4)
{
Swap(p1,p4);
p1++;
p4--;
}
}
int main()
{
char str[] = "1234abcdef";
int k = 21;
printf("%s\n",str);
rotate(str,k);
printf("%s\n",str);
return 0;
}
(3)把两个相同字符合并,建立双字符串,需要旋转k则从第k个开始取length个
//在一个字符串后面再跟一个相同字符串(创建双倍字符串)
#include<stdio.h>
#include<string.h>
#include<malloc.h>
void rotate(char *msg,int len,int k)
{
int step = k%len;
char *newStr = (char *)malloc(2*len+1);
strcpy(newStr,msg);
strcat(newStr,msg);
strncpy(msg,newStr+step,len);
free(newStr);
}
int main()
{
char msg[] = "1234abcdef";
int len = strlen(msg);
int k = 3;
printf("%s\n",msg);
rotate(msg,len,k);
printf("%s\n",msg);
return 0;
}