Element with highest occurence in array of strings - c++

Question

I need to find the element with the highest occurrence in an array of strings. I am not sure what to do, since I don't have much experience with this. I don't know pointers / hashtables.
I've already done this for integers, but I can't make it work for strings.
My version:
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
int a[]={1,2,3,4,4,4,5};
int n = sizeof(a)/sizeof(int );
int *b=new int [n];
fill_n(b,n,0); // Put n times 0 in b
int val=0; // Value that is the most frequent
for (int i=0;i<n;i++)
if( ++b[a[i]] >= b[val])
val = a[i];
cout<<val<<endl;
delete[] b;
return 0;
}
Any help for finding the most frequently occurring element in the array of strings is appreciated!

Answer 1

First, consider using C++ containers like vectors instead of plain arrays. (Search for "array to vector" or such to convert between them if you need.)
Then, if you can use C++11, you can do something like this (without C++11 it would become a bit more lengthy, but still doable):
std::string most_occurred(const std::vector<std::string> &vec) {
std::map<std::string,unsigned long> str_map;
for (const auto &str : vec)
++str_map[str];
typedef decltype(std::pair<std::string,unsigned long>()) pair_type;
auto comp = [](const pair_type &pair1, const pair_type &pair2) -> bool {
return pair1.second < pair2.second; };
return std::max_element(str_map.cbegin(), str_map.cend(), comp)->first;
}
Here is a version compatible with older C++
bool comp(const std::pair<std::string,unsigned long> &pair1,
const std::pair<std::string,unsigned long> &pair2) {
return pair1.second < pair2.second;
}
std::string most_occurred(const std::vector<std::string> &vec) {
std::map<std::string,unsigned long> str_map;
for (std::vector<std::string>::const_iterator it = vec.begin();
it != vec.end(); ++it)
++str_map[*it];
return std::max_element(str_map.begin(), str_map.end(), comp)->first;
}

Answer 2

You could consider using a vector of strings and to use a map to count occurrences:
#include <iostream>
#include <vector>
#include <map>
using namespace std;
int main(int argc, char *argv[])
{
vector<string> a;
map<string, int> m;
// fill a with strings
a.push_back("a");
a.push_back("b");
a.push_back("b");
a.push_back("c");
a.push_back("c");
a.push_back("c");
a.push_back("d");
a.push_back("e");
// count occurrences of every string
for (int i = 0; i < a.size(); i++)
{
map<string, int>::iterator it = m.find(a[i]);
if (it == m.end())
m.insert(pair<string, int>(a[i], 1));
else
m[a[i]] += 1;
}
// find the max
map<string, int>::iterator it = m.begin();
for (map<string, int>::iterator it2 = m.begin(); it2 != m.end(); ++it2)
{
if (it2 -> second > it -> second)
it = it2;
}
cout << it -> first << endl;
return 0;
}
This solution is probably not the best one in terms of elegance and efficiency, however it should give the idea.