定义两个字符串，用一个作为输入字符串，使用一个for语句计算长度，if语句判断出元音字母，使其变为0，再次使用if来改变大写为小写，使用一开始定义的字符串赋值，输出新的字符串并在前面加点
...

include<iostream>

using namespace std;
int main()
{
chars=new char[100];
chara= new char[100];
cin >> s;
int l;
for (l = 0; s[l] != '\0'; l++);
{
for (int i = 0; i < l; i++)
{
if (s[i] == 'A' || s[i] == 'E' || s[i] == 'I' || s[i] == 'O' || s[i] == 'U' || s[i] == 'Y' || s[i] == 'a' || s[i] == 'u' || s[i] == 'e' || s[i] == 'i' || s[i] == 'y'||s[i]=='o')
{
s[i] = '0';
}
else
{
if ('A' < s[i] && s[i] <= 'Z')
s[i] += 32;
}
}

}
int len = 0;
for (int i=0; i < l; i++)
{
    if ((s[i] > 'a'&&s[i] <= 'z') || (s[i] > 'A'&&s[i] <= 'Z'))
    {
        a[len] = s[i];
        len++;
    }
}
for (int i = 0; i < len; i++)
{
    cout << '.' << a[i];
}
return 0;

}
...