对称数是指从左到右和从右到左读数值相同的正整数，例如121、414是对称数，123不是对称数。对应代码段如下：

cout << "请输入正整数:";
cin >> n;

old_number = n;
new_number = 0;
while (n != 0){
    new_number = new_number * 10 + n % 10;
    n /= 10;
}

if (old_number == new_number)
    cout << "对称数";
else
    cout << "非对称数";