Task: Cheryl's birthday
C++: #include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

const vector<string> MONTHS = {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};

struct Birthday {
    int month, day;

    friend ostream &operator<<(ostream &, const Birthday &);
};

ostream &operator<<(ostream &out, const Birthday &birthday) {
    return out << MONTHS[birthday.month - 1] << ' ' << birthday.day;
}

template <typename C>
bool monthUniqueIn(const Birthday &b, const C &container) {
    auto it = cbegin(container);
    auto end = cend(container);
    int count = 0;
    while (it != end) {
        if (it->month == b.month) {
            count++;
        }
        it = next(it);
    }
    return count == 1;
}

template <typename C>
bool dayUniqueIn(const Birthday &b, const C &container) {
    auto it = cbegin(container);
    auto end = cend(container);
    int count = 0;
    while (it != end) {
        if (it->day == b.day) {
            count++;
        }
        it = next(it);
    }
    return count == 1;
}

template <typename C>
bool monthWithUniqueDayIn(const Birthday &b, const C &container) {
    auto it = cbegin(container);
    auto end = cend(container);
    while (it != end) {
        if (it->month == b.month && dayUniqueIn(*it, container)) {
            return true;
        }
        it = next(it);
    }
    return false;
}

int main() {
    vector<Birthday> choices = {
        {5, 15}, {5, 16}, {5, 19}, {6, 17}, {6, 18},
        {7, 14}, {7, 16}, {8, 14}, {8, 15}, {8, 17},
    };

    
    
    vector<Birthday> filtered;
    for (auto bd : choices) {
        if (!monthUniqueIn(bd, choices)) {
            filtered.push_back(bd);
        }
    }

    
    
    vector<Birthday> filtered2;
    for (auto bd : filtered) {
        if (!monthWithUniqueDayIn(bd, filtered)) {
            filtered2.push_back(bd);
        }
    }

    
    
    vector<Birthday> filtered3;
    for (auto bd : filtered2) {
        if (dayUniqueIn(bd, filtered2)) {
            filtered3.push_back(bd);
        }
    }

    
    
    vector<Birthday> filtered4;
    for (auto bd : filtered3) {
        if (monthUniqueIn(bd, filtered3)) {
            filtered4.push_back(bd);
        }
    }

    if (filtered4.size() == 1) {
        cout << "Cheryl's birthday is " << filtered4[0] << '\n';
    } else {
        cout << "Something went wrong!\n";
    }

    return 0;
}

VB: Private Sub exclude_unique_days(w As Collection)
    Dim number_of_dates(31) As Integer
    Dim months_to_exclude As New Collection
    For Each v In w
        number_of_dates(v(1)) = number_of_dates(v(1)) + 1
    Next v
    For i = w.Count To 1 Step -1
        If number_of_dates(w(i)(1)) = 1 Then
            months_to_exclude.Add w(i)(0)
            w.Remove i
        End If
    Next i
    For Each m In months_to_exclude
        exclude_month w, m
    Next m
End Sub
Private Sub exclude_month(x As Collection, v As Variant)
    For i = x.Count To 1 Step -1
        If x(i)(0) = v Then x.Remove i
    Next i
End Sub
Private Sub exclude_non_unique_days(w As Collection)
    Dim number_of_dates(31) As Integer
    For Each v In w
        number_of_dates(v(1)) = number_of_dates(v(1)) + 1
    Next v
    For i = w.Count To 1 Step -1
        If number_of_dates(w(i)(1)) > 1 Then
            w.Remove i
        End If
    Next i
End Sub
Private Sub exclude_non_unique_months(w As Collection)
    Dim months As New Collection
    For Each v In w
        On Error GoTo 1
        months.Add v(0), v(0)
    Next v
1:
    For i = w.Count To 1 Step -1
        If w(i)(0) = v(0) Then
            w.Remove i
        End If
    Next i
End Sub
Public Sub cherylsbirthday()
    Dim v As New Collection
    s = "May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, August 17"
    t = Split(s, ",")
    For Each u In t
        v.Add Split(Trim(u), " ")
    Next u
    
    exclude_unique_days v
    
    exclude_non_unique_days v
    
    exclude_non_unique_months v
    Debug.Print v(1)(0); " "; v(1)(1)
End Sub