字符串最小表示法

int getPos(string  s,int op)//zero represent the least representation, while one represent the largest
{
    int i=0,j=1;
    int len=s.size();
    while (i<len&&j<len)
    {
        int k=0;
        while (k<len&&s[(i+k)%len]==s[(j+k)%len]) k++;
        if (k>=len) break;
        if ((s[(i+k)%len]<s[(j+k)%len])^op) i+=k+1;
        else j+=k+1;
        if(i==j) j++;
    }
    return i<j?i:j;
}