这是基础的数位拆分，当然也能用字符串

#include <bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    cin >> n;
    int a[10], cnt = 0;
    while (n)
    {
        a[++cnt] = n % 10;
        n /= 10;
    }
    cout << cnt << endl;
    for (int i = cnt; i >= 1; i--)
        cout << a[i] << " ";
    cout << endl;
    for (int i = 1; i <= cnt; i++)
        cout << a[i];
    cout << endl;
    return 0;
}

我来

#include<bits/stdc++.h>
using namespace std;
int n,a[10],sum;
int main()
{
    cin>>n;
    while(n>0)
    {
        sum++;
        a[sum]=n%10;
        n/=10;
    }
    cout<<sum<<endl;
    for(int i=sum;i>=1;i--)
    {
        cout<<a[i]<<" ";
    }
    cout<<endl;
    for(int i=1;i<=sum;i++)
    {
        cout<<a[i];
    }
    return 0;
}

AC先赞后搬

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int n, s = 0, c = 0;
	cin >> n;
	//求n倒过来的数，求n的位数；
	while(n != 0){
		s = s*10 + n%10;
		n /= 10;
		c++;
	} 
	cout << c << endl;
	//求s倒过来的数
	int t = s;
	while(t != 0){
		cout << t%10 << " ";
		t /= 10;
	} 
	cout << endl;
	cout << s << endl;
	return 0;
}