最长反身子串

给定一个字串X，求它最长字串S，使得S=SR，SR为S的反序，即如果S=abc，则SR=cba
例子：X=abccba，则输出S=abccba

遍历X的子串，从最长子串开始，对每一个子串判断其是否为反身字串，是则找到所需字串

bool IsReverseString(const char *str, int s, int len)
{
    const char *start = str+s,  *end=str+s+len-1;
    while ( start <= end)
    {
        if (*start== *end)
        {
            start++, end--;
        }
        else
            break;
    }
    if (start >= end)
        return true;
    else
        return false;

}

void PrintRS(const char *str, int s, int len)
{
    const char *start = str+s,  *end = str+s+len-1;
    while (start != end)
        printf("%c",*start++);
    printf("%c", *start);
    printf("\n");
}
void LongReverseString(const char *str)
{
    int len = strlen(str);
    int curlen = len;
    while (curlen >=3)
    {
        int i=0;
        while (i<=len-curlen)
        {
            if (IsReverseString(str, i, curlen))
            {
                PrintRS(str, i, curlen);
                return;
            }
            i++;
        }
        curlen--;
    }
}