code bằng C++:

`+` Ngày hợp lệ

`+` Số bin bon

#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
bool check (long long n)
{
    for (long long i = 2; i <= sqrt(n);++i)
    {
        if (n % i == 0) return false;
    }
    return n > 1;
}
long long tcs (string s)
{
    long long cnt = 0;
    for (long long i = 0; i < s . size(): ++i) cnt += s[i] - '0';
    return cnt;
}
long long maxcs(string s)
{
    int mx = -100000;
    for (long long i = 0; i < s . size(); ++i)
    {
        mx = max(mx , s[i] - '0');
    }
    return mx;
}
string a[1000005];
long long n, t = 0;
int main()
{
    cin >> n;
    for (long long i = 1; i <= n; ++i)
    {
        cin >> a[i];
    }
    for (long long i = 1; i <= n; ++i)
    {
        t = tcs(a[i]) * 10;
        t = t + maxcs(a[i]);
        if (check(t)) cout << "YES\n";
        else cout << "NO\n";
        t = 0;
    }
}

#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
bool nhuan(int y)
{
    return (y%4==0 and y%100 != 0) || (y%400==0);
}
bool check(int d, int m, int y)
{
    if (m < 1 || m > 12 || d < 1 || d > 31 || y < 1 || y > 3000) return false;
    if (m == 2)
    {
        if (nhuan(y) and d > 29) return false;
        if (!nhuan(y) and d > 28) return false;
    }
    if (m == 4 || m == 6 || m == 9 || m == 11)
    {
        if (d > 30) return false;
    }
    return true;
}
int tt;
int main()
{
    cin >> tt;
    while (tt--)
    {
        int d,m,y;
        cin >> d >> m >> y;
        cout << (check(d, m, y) ? "TRUE" : "FALSE") << '\n';
    }
}
    

`+`Ngày hợp lệ

#include <iostream>
using namespace std;
int main() {
int t;
cin>>t;
while (t--) {
int d,m,y;
cin>>d>>m>>y;
bool ok=true;
if (m<1 || m>12 ||d<1 || y<1 || y>3000)
ok=false;
else {
if (m==2) {
if ((y%4==0 && y%100!=0) || (y%400==0)) {
if (d>29)
ok=false;
} else {
if (d>28)
ok=false;
}
} else if (m==4 || m==6 || m==9 || m==11) {
if (d>30)
ok=false;
} else {
if (d>31)
ok=false;
}
}
cout<<(ok?"TRUE":"FALSE")<<'\n';
}
return 0;
}

`+` Số bin bon

#include <iostream>
#include <string>
using namespace std;
bool ok(int n) {
if (n<=1) 
return false;
if (n<=3) 
return true;
if (n%2==0 || n%3==0) 
return false;
for (int i=5;i*i<=n;i+=6) {
if (n%i==0 || n%(i+2)==0)
return false;
}
return true;
}
int main() {
int t;
cin>>t;
while (t--) {
string n;
cin>>n;
int t2=0;
char max='0';
for (char c:n) {
t2+=(c-'0');
if (c>max) {
max=c;
}
}
int k=t2*10+(max-'0');
if (ok(k)) {
cout<<"YES\n";
} else {
cout<<"NO\n";
}
}
return 0;
}