Bjarne Stroustrup “Programming Principles and Practice Using C++” Chapter 4 Exercise 16
Using std_lib_facilities.h by Bjarne Stroustrup.

// Philipp Siedler
// Bjarne Stroustrup's PP
// Chapter 4 Exercise 16
#include "std_lib_facilities.h"
int main()
try
{
vector<int> seriesNum;
int singleNum;
int counterTemp = 0;
int countHighest = 0;
int indexHighest = 0;
string noNum = " ";
bool check1 = true;
cout << "Enter a series of numbers equal or larger to one, enter 0 to end the series" << "\n";
while (check1 == true) {
cout << "Enter number for series\n";
cin.clear();
if (cin >> singleNum) {
if (singleNum > 0) {
seriesNum.push_back(singleNum);
}
else if (singleNum == 0) {
check1 = false;
break;
cout << "test";
}
}
else {
cin.clear();
cin >> noNum;
error("Entry was not a number", noNum);
}
}
sort(seriesNum);
for (int i = 0; i < seriesNum.size(); i++) {
cout << seriesNum[i] << " ";
}
for (int i = 1; i < seriesNum.size(); i++) {
if (seriesNum[i] == seriesNum[i - 1]) {
counterTemp++;
}
else {
counterTemp = 0;
}
if (counterTemp > countHighest) {
indexHighest = i-1;
countHighest = counterTemp;
}
}
cout << "The Mode of numSeries is: " << seriesNum[indexHighest] << " counted " << countHighest+1 << " times\n";
keep_window_open(".");
}
catch (runtime_error e) {
cout << e.what() << "\n";
keep_window_open(".");
}
catch(...) {
cout << "Exiting!\n";
keep_window_open(".");
}

Output:
Enter a series of numbers equal or larger to 1, enter 0 to end the series
Enter number for series
2
Enter number for series
4
Enter number for series
5
Enter number for series
3
Enter number for series
4
Enter number for series
4
Enter number for series
3
Enter number for series
2
Enter number for series
0
2 2 3 3 4 4 4 5 The Mode of numSeries is: 4 counted 3 times
Please enter . to exit