修改代码倒序输出一个三位整数 c++

#include<bits/stdc++.h>
using namespace std;
int main(){
int n,a,b,c;
cin>>n;
a==n%10;
b==n%10%10;
c==n%10/10;
cout<<a,b,c;
return 0;
}

int main
{
int n,a,b,c;
std::cin>>n;
a=n/100;
b=(n-a100)/10;
c=n-a100-b*10;
std::cout<<c<<b<<a;
return 0;
}

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>

using namespace std;

int main()
{
    int n;
    cin >> n;
    if (n < 0)
    {
        cerr << "requires n >= 0\n";
        return 1;
    }
    vector<int> digits;
    if (n == 0)
        digits.push_back(0);
    while (n)
    {
        digits.push_back(n % 10);
        n /= 10;
    }
    copy(digits.begin(), digits.end(), ostream_iterator<int>(cout));
    return 0;
}