Throwing an instance of "out of range" in c++ - c++

Question

When i build and run the code, i get the next error: "terminate called after throwing an instance of 'std::out_of_range'
what<>: vector::_M_range_check: __n <which is 0> >= this->size<> <which is 0>
I don't know how to fix this problem, I am new to coding!
What I'm trying to do is using a collection (list) of integers and allowing the user to select options from a menu to perform operations on the list.
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
vector <int>numbers{};
int nr_to_add{};
char selection{};
double average{};
int min = numbers.at(0);
int max = numbers.at(0);
do{
cout << "P - Print numbers!" << endl;
cout << "A - Add numbers!" << endl;
cout << "M - Display mean of the numbers!" << endl;
cout << "S - Display the smallest number!" << endl;
cout << "L - Display the largest number!" << endl;
cout << "Q - Quit" << endl;
cout << "Enter your selection: ";
cin >> selection;
if(selection == 'p' || selection == 'P'){
for(int i = 0; i < numbers.size(); i++)
cout << "The numbers are: " << numbers[i];
if(numbers.empty())
cout << "[] - the list is empty! " << "\nYou should add some numbers!" << endl;
cout << "Add some numbers: ";
cin >> nr_to_add;
numbers.push_back(nr_to_add);
}else if(selection == 'a' || selection == 'A'){
cout << "Add the number you want: ";
cin >> nr_to_add;
cout << "\n" << nr_to_add << " has been added successfully!" << endl;
numbers.push_back(nr_to_add);
}else if(selection == 'm' || selection == 'M'){
if(numbers.empty())
cout << "Unable to calculate de average - no data introduced!" << endl;
if(numbers.size() != 0)
average = accumulate(numbers.begin(),numbers.end(), 0.0)/numbers.size();
cout << "The average is: " << average << endl;
}else if(selection == 's' || selection == 'S'){
if(numbers.empty())
cout << "Unable to determine the smallest number - list is empty!";
if(numbers.size() != 0)
for(int i = 0,n = 0; i <= n; i++){
if(numbers.at(i) < min)
min = numbers[i];
cout << "The smallest number is: " << min << endl;
}
}else if(selection == 'l' || selection == 'L'){
if(numbers.empty())
cout << "Unable to determine the largest number - list is empty!";
if(numbers.size() != 0)
for(int i = 0,n = 0; i <= n; i++){
if(numbers.at(i) > max)
max = numbers[i];
cout << "The largest number is: " << max << endl;
}
}else if(selection == 'q' || selection == 'Q'){
cout << "Goodbye..." << endl;
} else {
cout << "Unknown selection, please try again" << endl;
}
} while(selection != 'q' && selection != 'Q');
return 0;
}

Answer 1

The problem is that you are calling at(0) on an empty vector. That is what the out_of_range error is telling you. You need to move the calls into your if statements where the values are actually being used, after you perform your empty() checks.
Also, your min and max loops are coded wrong. And you don't need to use loops at all, you can use the standard std::min_element() and std::max_element() algorithms instead (you are already using the std::accumulate() algorithm).
Try something more like this:
#include <iostream>
#include <vector>
#include <algorithm>
#include <numeric>
#include <limits>
using namespace std;
int main()
{
vector<int> numbers{};
int nr_to_add;
char selection;
double average_nr;
int min_nr, max_nr;
do {
cout << "P - Print numbers!" << endl;
cout << "A - Add numbers!" << endl;
cout << "M - Display mean of the numbers!" << endl;
cout << "S - Display the smallest number!" << endl;
cout << "L - Display the largest number!" << endl;
cout << "Q - Quit" << endl;
cout << "Enter your selection: ";
if (!(cin >> selection)) {
selection = '\0';
cin.clear();
}
cin.ignore(numeric_limits<streamsize>::max(), '\n');
if (selection == 'p' || selection == 'P') {
if (numbers.empty()) {
cout << "The list is empty! " << "\nYou should add some numbers!" << endl;
} else {
cout << "The numbers are:"
for(size_t i = 0; i < numbers.size(); ++i) {
cout << " " << numbers[i];
}
cout << endl;
}
}
else if (selection == 'a' || selection == 'A') {
cout << "Add the number you want: ";
if (cin >> nr_to_add) {
numbers.push_back(nr_to_add);
cout << "\n" << nr_to_add << " has been added successfully!" << endl;
} else {
cout << "Bad input, please try again" << endl;
cin.clear();
}
cin.ignore(numeric_limits<streamsize>::max(), '\n');
}
else if (selection == 'm' || selection == 'M'){
if (numbers.empty()) {
cout << "Unable to calculate the average - list is empty!" << endl;
} else {
average_nr = accumulate(numbers.begin(), numbers.end(), 0.0) / numbers.size();
cout << "The average is: " << average_nr << endl;
}
}
else if (selection == 's' || selection == 'S') {
if (numbers.empty()) {
cout << "Unable to determine the smallest number - list is empty!";
} else {
/*
min_nr = numbers[0];
for(size_t i = 1; i < numbers.size(); ++i){
if (numbers[i] < min_nr) {
min_nr = numbers[i];
}
}
*/
min_nr = *min_element(numbers.begin(), numbers.end());
cout << "The smallest number is: " << min_nr << endl;
}
}
else if (selection == 'l' || selection == 'L') {
if (numbers.empty()) {
cout << "Unable to determine the largest number - list is empty!";
} else {
/*
max_nr = numbers[0];
for(size_t i = 1; i < numbers.size(); ++i){
if (numbers[i] > max_nr) {
max_nr = numbers[i];
}
}
*/
max_nr = *max_element(numbers.begin(), numbers.end());
cout << "The largest number is: " << max_nr << endl;
}
}
else if (selection == 'q' || selection == 'Q') {
cout << "Goodbye..." << endl;
}
else {
cout << "Unknown selection, please try again" << endl;
}
}
while (selection != 'q' && selection != 'Q');
return 0;
}

Answer 2

Try this
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
vector <int>numbers{};
int nr_to_add{};
char selection{};
double average{};
int min = 0;
int max = 0;
do {
cout << "P - Print numbers!" << endl;
cout << "A - Add numbers!" << endl;
cout << "M - Display mean of the numbers!" << endl;
cout << "S - Display the smallest number!" << endl;
cout << "L - Display the largest number!" << endl;
cout << "Q - Quit" << endl;
cout << "Enter your selection: ";
cin >> selection;
if (selection == 'p' || selection == 'P') {
for (int i = 0; i < numbers.size(); i++)
cout << "The numbers are: " << numbers[i];
if (numbers.empty()) {
cout << "[] - the list is empty! " << "\nYou should add some numbers!" << endl;
cout << "Add some numbers: ";
cin >> nr_to_add;
numbers.push_back(nr_to_add);
min = nr_to_add;
max = nr_to_add;
}
}
else if (selection == 'a' || selection == 'A') {
cout << "Add the number you want: ";
cin >> nr_to_add;
cout << "\n" << nr_to_add << " has been added successfully!" << endl;
if (numbers.empty) {
min = nr_to_add;
max = nr_to_add;
}
else {
if (min > nr_to_add) min = nr_to_add;
if (max < nr_to_add) max = nr_to_add;
}
numbers.push_back(nr_to_add);
}
else if (selection == 'm' || selection == 'M') {
if (numbers.empty())
cout << "Unable to calculate de average - no data introduced!" << endl;
if (numbers.size() != 0)
average = accumulate(numbers.begin(), numbers.end(), 0.0) / numbers.size();
cout << "The average is: " << average << endl;
}
else if (selection == 's' || selection == 'S') {
if (numbers.empty())
cout << "Unable to determine the smallest number - list is empty!";
else
cout << "The smallest number is: " << min << endl;
}
else if (selection == 'l' || selection == 'L') {
if (numbers.empty())
cout << "Unable to determine the largest number - list is empty!";
else
cout << "The largest number is: " << max << endl;
}
else if (selection == 'q' || selection == 'Q') {
cout << "Goodbye..." << endl;
}
else {
cout << "Unknown selection, please try again" << endl;
}
} while (selection != 'q' && selection != 'Q');
return 0;