C++ most frequent element in map - c++

Question

I made a program that takes data from file, puts it into vector and then checks for most frequent element in the vector. (using map)
The problem is when I have same number of elements in the data (two Element1, two Element2, one Element3). It returns Element1 and I need it to pass the information that there is "no most frequent element".
My code looks like:
using namespace std;
bool comp(const pair<string, unsigned long> &pair1,
const pair<string, unsigned long> &pair2) {
return pair1.second < pair2.second;
}
string Odczyt::tokenizer() {
inFile.open("baza.txt");
while (!inFile.eof()) {
for (int i = 0; i < 4; i++) {
inFile >> row1[i] >> row2[i] >> row3[i] >> row4[i];
}
}
sVector1.assign(row1, row1 + 3);
string w1 = most_occurred(sVector1);
return w1;
}
string Odczyt::most_occurred(vector<string> &vec) {
map<string, unsigned long> str_map1;
for (vector<string>::const_iterator it = vec.begin(); it != vec.end();
++it) {
++str_map1[*it];
}
return max_element(str_map1.begin(), str_map1.end(), comp)->first;
}

Answer 1

Create a variable which stores the number of times you have found an element which occurs m times (where m is the current maximum number of times any element has occurred). If at the termination point of the algorithm you have more than one element appearing m times, then you know there is no single most-frequently-occurring element.

Answer 2

#include <iostream>
#include <string>
#include <vector>
#include <map>
using namespace std;
string most_occurred(vector<string> &vec) {
map<string, unsigned long> str_map1;
std::string max_element = "";
int max_count = 0;
typedef vector<string>::const_iterator iter;
iter end = vec.end();
for (iter it = vec.begin(); it != end; ++it) {
int count = ++str_map1[*it];
if(count == max_count) max_element = "no max found";
if(count > max_count) {
max_count = count;
max_element = *it;
}
}
return max_element;
}
int main() {
std::string arr1[5] = {"aa" , "bb", "cc", "dd", "ee"}; // no max found
std::string arr2[5] = {"aa" , "aa", "cc", "dd", "ee"};// aa
std::string arr3[5] = {"aa" , "aa", "cc", "cc", "ee"}; // no max found
std::vector<std::string> input1(arr1, arr1+5);
std::vector<std::string> input2(arr2, arr2+5);
std::vector<std::string> input3(arr3, arr3+5);
std::cout << most_occurred(input1) << std::endl;
std::cout << most_occurred(input2) << std::endl;
std::cout << most_occurred(input3) << std::endl;
}
the result is:
no max found
aa
no max found
The following test resulted in no max found.
int main() {
std::string arr1[24] = {"Element1", "Element2", "Element33", "1",
"Element1", "Element2", "Element33", "2", "Element11", "Element2",
"Element33", "2", "Element11" "Element21" "Element31", "2", "Element11",
"Element21", "Element31", "1", "Element12", "Element21", "Element31",
"1"}; // no max found
std::vector<std::string> input1(arr1, arr1+24);
std::cout << most_occurred(input1) << std::endl;
}
If the above code returns std::string("") then there was no max element, else it will return the max.

Answer 3

This is a frequent operation here is my sample code:
#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <iterator>
using namespace std;
int main(int argc, char* argv[]) {
// number -> frequency
map<int, int> idfreq = {{1, 3}, {2, 10}, {3,8}, {9, 15}, {7,30}};
vector<pair<int, int> > v;
copy(idfreq.begin(), idfreq.end(), back_inserter(v));
for (auto& el : v) {
cout << el.first << " " << el.second << endl;
}
cout << endl;
make_heap(v.begin(), v.end(), [](const pair<int,int> &a, const pair<int,int> &b){ return a.second < b.second; });
// with -std=c++14
//make_heap(v.begin(), v.end(), [](auto& a, auto& b){ return a.second < b.second; });
cout << v.front().first << " " << v.front().second << " most frequent element\n";
cout << "after make heap call\n";
for (auto& el : v) {
cout << el.first << " " << el.second << endl;
}
cout << endl;
return 0;
}