Linked List Help!! (Now have 23 errors with code)

[againtry]

@OP A few small changes to make yours work. Just put the functions back in one at a time and test as you go.

#include <iostream>

int main() {
    char userAnswer{};
    
    do {
        std::cout << "\nA--Add a month of statistics\n"
        << "E--Edit a month of statistics\n"
        << "P--Print report\n"
        << "Q--Quit\n"
        << "Choice: ";
        
        std::cin >> userAnswer;
        userAnswer = toupper(userAnswer); // <--
        
        int m{0}; // <---
        switch (toupper(userAnswer))
        {
            case 'A':
                std::cout << "Enter month: ";
                std::cout << "Enter rainfall (in Inches): ";
                break;
            case 'E':
                std::cout << "Enter month: 0 or 1(error)";
                std::cin >> m;
                
                if (m==0)
                {
                    std::cout << "Enter new rainfall (in Inches): ";
                }
                else
                    std::cout << "ERROR: Invalid Month\n";
                break;
            case 'P':
                std::cout << "Total rainfall: " ;
                std::cout << "Average rainfall: " ;
                std::cout << "Highest rainfall: " ;
                std::cout << "Lowest rainfall: " ;
                break;
            case 'Q':
                std::cout << "Quitter\n";
                break;
            default:
                std::cout << "Bad answer\n";
        }
    } while ( userAnswer != 'Q');
    
    std::cout << "That's it!\n";
    return 0;
}

[seeplus]

Even the best screw up code. I once had a summer job at the university getting some code the Professor of Programming had written to work! (which he then proceeded to present as his own the next term!) He was great on writing complicated flowcharts but less so on actually writing the code. I later found out his doctorate was in financial modelling using a computer...... He was a self-taught programmer. Great ideas man. Guess that's what got him his job.

what about a variable declared before the do loop; some calcs are done in the body; then that value is part of the while condition?

In this case the value used in the while condition is the value set in the body as it's defined outside the body. The confusion can come when a variable is defined before the do loop and also within the body. In this case the value of the variable before the do is used in the while condition.

int a = 1;

do {
    int a {};
    std::cin >> a;
} while (a > 0);

This is an infinite loop as the value of a defined within the do body end scope at the }. The value of a used in while is always 1 !

What we really want is something like this:

do (int a{}) {
    std::cin >> a;
} while (a > 0);

but also not yet in the standard. If we want this we have to do:

{
    int a {};

    do {
        std::cin >> a;
    } while (a > 0);
}

[againtry]

Hence int m{0}; // <--- with https://stackoverflow.com/questions/5685471/error-jump-to-case-label/5685578 as one example discussing it.

[againtry]

@OP
Needs to be completed but it doesn't bomb.
Also note that by decoupling the data from the list life is a little bit simpler.
It might be useful in making it clearer on that point to remove the name 'Rainfall' from the code/methods etc. The Data is simply a combination of an int (or double - an inch of rain is a lot of rain) and a string for the month name to improve flexibility and reusability.

#include <iostream>
#include <string>

struct Data
{
    double number{0};
    std::string name;
    
    void setNumber(double aNumber){number = aNumber;}
    void setName(std::string aName){name = aName;}
    
    Data operator+ (const Data& dat)
    { return { dat.number + this->number, "SUM"}; }
    
    bool operator== (const Data& rhs) const
    { return this -> number == rhs.number; }
    
    bool operator<= (const Data& rhs)
    { return this -> number <= rhs.number; }
    
    bool operator>= (const Data& rhs)
    { return this -> number >= rhs.number; }
    
    friend std::ostream& operator<<(std::ostream& os, const Data& dat)
    { os << '(' << dat.number << ' ' << dat.name << ')'; return os; }
};

class List
{
private:
    struct node
    {
        Data item; // Store the data of each node
        node* next; // Will point to the next node in the list
    };
    
    typedef struct node* nodePtr;
    
    nodePtr head; // head of node
    nodePtr temp; // temprary node
    nodePtr curr; // current node
    
public:
    List();
    void addNode(Data);
    void deleteNode(Data);
    void printList();
    
    //void appendNode(Data);
    void displayList() const;
    Data getHighestRainfall() const;
    Data getLowestRainfall() const;
    Data getTotal() const;
};

List::List()
{
    head = nullptr;
    temp = nullptr;
    curr = nullptr;
}

void List::addNode(Data dat)
{
    nodePtr n = new node; // node pointer equals new node
    n->next = nullptr;
    n->item = dat;
    
    if (head != nullptr)
    {
        curr = head;
        while (curr->next != nullptr)
        {
            curr = curr->next;
        }
        curr->next = n;
    }
    else
    {
        head = n;
    }
}

void List::deleteNode(Data dat) {
    nodePtr delPtr = nullptr;
    temp = head;
    curr = head;
    
    while (curr != nullptr && !(curr->item == dat) )
    {
        temp = curr;
        curr = curr->next;
    }
    
    if (curr == NULL) {
        std::cout << dat << "was not in the list\n";
        delete delPtr;
    }
    else {
        delPtr = curr;
        curr = curr->next;
        temp->next = curr;
        if (delPtr == head) {
            head = head->next;
            temp = NULL;
        }
        delete delPtr;
        std::cout << "The value " << dat << "was deleted\n";
    }
}

void List::printList() {
    curr = head;
    while (curr != nullptr) {
        std::cout << curr->item << std::endl;
        curr = curr->next;
    }
}

Data List::getLowestRainfall() const
{
    nodePtr np = head;
    Data lowest = np->item;
    
    while (np)
    {
        if (np->item <= lowest)
            lowest = np->item;
        np = np->next;
    }
    
    return lowest;
}

Data List::getHighestRainfall() const
{
    nodePtr np = head;
    Data highest = np->item;
    
    while (np)
    {
        if (np->item >= highest)
            highest = np->item;
        np = np->next;
    }
    
    return highest;
}

Data List::getTotal() const
{
    nodePtr np = head;
    Data total = np->item;
    
    while (np)
    {
        
        total = total + np->item;
        np = np->next;
    }
    
    return total;
}

void List::displayList() const
{
    nodePtr np = head;
    
    while (np)
    {
        std::cout << "Element " << np->item;
        np = np->next;
    }
}

int main()
{
    // SETUP SOME DATA
    Data year_2021[]
    {
        {12, "Jan"}, {34, "Feb"}, {56, "Mar"}, {1,"Apr"}, {7,"May"}, {32,"Jun"},
        {7,"Jul"},{3,"Aug"},{1,"Sep"}, {5,"Oct"},{30,"Nov"},{7,"Dec"}
    };
    size_t SIZE = sizeof(year_2021)/ sizeof(Data);
    
    // CREATE AND POPULATE A LIST
    List rainfall_record;
    for(int i = 0; i < SIZE; i++){ rainfall_record.addNode( year_2021[i] ); }
    
    // SOME TESTS
    rainfall_record.displayList();
    std::cout << year_2021[2] + year_2021[4] + year_2021[5];
    std::cout << "Minimum: " << rainfall_record.getLowestRainfall();
    std::cout << "Maximum: " << rainfall_record.getHighestRainfall();
    std::cout << rainfall_record.getTotal();
    
    Data clone = year_2021[3];
    std::cout << clone << '\n';
    
    
    // MENU STUFF
    char userAnswer{};
    
    do {
        std::cout
        << '\n'
        << "A--Add a month of statistics\n"
        << "E--Edit a month of statistics\n"
        << "P--Print report\n"
        << "Q--Quit\n"
        << "Choice: ";
        
        std::cin >> userAnswer;
        userAnswer = toupper(userAnswer); // <--
        
        int m{0}; // <---
        Data temp;
        
        switch (toupper(userAnswer))
        {
            case 'A':
                std::cout << "Enter month: ";
                std::cin >> temp.name;
                
                std::cout << "Enter rainfall (in Inches): ";
                std::cin >> temp.number;
                rainfall_record.addNode(temp);
                break;
            case 'E':
                std::cout << "Enter month: 0 or 1(error)";
                std::cin >> m;
                
                if (m==0)
                {
                    std::cout << "Enter new rainfall (in Inches): ";
                }
                else
                    std::cout << "ERROR: Invalid Month\n";
                break;
            case 'P':
                std::cout << "FULL LIST: ";
                rainfall_record.displayList();
                std::cout << "  Total rainfall: " << rainfall_record.getTotal() << '\n';
                std::cout << "Highest rainfall: " << rainfall_record.getHighestRainfall() << '\n';
                std::cout << " Lowest rainfall: " << rainfall_record.getLowestRainfall() << '\n';
                break;
            case 'Q':
                std::cout << "Quitter\n";
                break;
            default:
                std::cout << "Bad answer\n";
        }
    } while ( userAnswer != 'Q');
    
    std::cout << "That's it!\n";
    return 0;
}

Element (12 Jan)Element (34 Feb)Element (56 Mar)
Element (1 Apr)Element (7 May)Element (32 Jun)
Element (7 Jul)Element (3 Aug)Element (1 Sep)
Element (5 Oct)Element (30 Nov)
Element (7 Dec)
(95 SUM)
Minimum: (1 Sep)
Maximum: (56 Mar)(207 SUM)(1 Apr)

A--Add a month of statistics
E--Edit a month of statistics
P--Print report
Q--Quit
Choice: a
Enter month: January
Enter rainfall (in Inches): 999

A--Add a month of statistics
E--Edit a month of statistics
P--Print report
Q--Quit
Choice: p
FULL LIST: Element (12 Jan)Element (34 Feb)Element (56 Mar)
Element (1 Apr)Element (7 May)Element (32 Jun)Element (7 Jul)
Element (3 Aug)Element (1 Sep)Element (5 Oct)
Element (30 Nov)Element (7 Dec)Element (999 January)  
Total rainfall: (1206 SUM)
Highest rainfall: (999 January)
 Lowest rainfall: (1 Sep)

A--Add a month of statistics
E--Edit a month of statistics
P--Print report
Q--Quit
Choice: Q
Quitter
That's it!
Program ended with exit code: 0