#include <iostream>
#include <vector>
#include <unordered_map>
// Function to group elements by their first occurrence
std::vector<int> groupElements(const std::vector<int>& vec) {
std::unordered_map<int, int> frequencyMap; // To store the frequency of each element
std::vector<int> result; // To store the grouped elements
std::vector<int> order; // To maintain the order of first occurrences
// Count frequencies and track the order of first occurrences
for (int num : vec) {
if (frequencyMap.find(num) == frequencyMap.end()) {
order.push_back(num); // Add to order if it's the first occurrence
}
frequencyMap[num]++;
}
// Group elements based on their first occurrence
for (int num : order) {
for (int i = 0; i < frequencyMap[num]; i++) {
result.push_back(num);
}
}
return result;
}
int main() {
std::vector<int> vec = {88, 33, 77, 88, 22, 55, 88, 55, 11, 99, 88, 11, 77};
// Group elements
std::vector<int> groupedVector = groupElements(vec);
// Output the grouped vector
std::cout << "Grouped vector: ";
for (int num : groupedVector) {
std::cout << num << " ";
}
std::cout << std::endl;
}
/*
run:
Grouped vector: 88 88 88 88 33 77 77 22 55 55 11 11 99
*/
