#include
#include
#define false 0
#define true 1
/*判断一个字符串是不是回环字符串函数*/
int isok(char *str)
{
int len = strlen(str);
int i = 0, j = len – 1;
while (i < j)
{
if(str[i] != str[j])
return false;
i++; j–;
}
return true;
}
/*如果不是回环字符串，在字符串的头部添加字符串，让这个字符串成为回环字符串*/
int addhead(char *str)
{
int len = strlen(str);
printf(“str num = %d\n”,len);
char tmp[2*len];
int pos = 0, j = len – 1;
while(pos < len -1)
{
tmp[pos++] = str[j--];
printf(“xun huan\n”);
}
tmp[pos] = ‘\0′;
strncat(tmp,str,len);
printf(“tmp string is %s\n”,tmp);
if(isok(tmp))
printf(“successful \n”);
}
/*如果不是回环字符串，在函数的尾部添加字符串，让这个字符串成为回环字符串*/
int addtail(char *str)
{
int len = strlen(str);
int i=0, k=0,j;
char tmp[2*len];
while (i < len )
{
tmp[i++] = str[k++];
}
j = i;
i = 0;
k = len – 1;
while(i < len -1)
{
tmp[j++] = str[k--];
}
tmp[j] = ‘\0′;
printf(“tmp = %s\n”, tmp);
if(isok(tmp))
printf(“successful \n”);
}
/*测试回环函数的主函数*/
int main(int argc, char *argv[])
{
char *str = “abc”;
int num = isok(str);
if(num == 1)
{
printf(“this is string\n”);
}
else {
printf(“this is the not string\n”);
num = addhead(str);
num = addtail(str);
}
return 0;
}