bool oneDistance(string s1, string s2){    if (s1.length()<s2.length())    {        swap(s1, s2);    }    if (s1.length() - s2.length() >1)        return false;    bool replace = true;    if (s1.length() != s2.length())    {        replace = false;    }    int times = 0;    for (int i = 0, j = 0; j < s1.length();)    {        if (i == s2.length() || s1[j] != s2[i])        {            times += 1;            if (times>1)                return false;            if (replace)            {                continue;            }            else            {                ++j;            }        }        else        {            ++i;            ++j;        }    }    return true;} int main(){    auto r = oneDistance("atc", "at");}