Finding the max value in a map

Solution 1:

You can use std::max_element to find the highest map value (the following code requires C++11):

std::map<int, size_t> frequencyCount;
using pair_type = decltype(frequencyCount)::value_type;

for (auto i : v)
    frequencyCount[i]++;

auto pr = std::max_element
(
    std::begin(frequencyCount), std::end(frequencyCount),
    [] (const pair_type & p1, const pair_type & p2) {
        return p1.second < p2.second;
    }
);
std::cout << "A mode of the vector: " << pr->first << '\n';

Solution 2:

This can be done in few lines, here's a full working snippet:

#include <iostream>
#include <algorithm>
#include <map>
int main() {
    std::map<char,int> x = { { 'a',1 },{ 'b',2 },{'c',0} };
    std::map<char,int>::iterator best
        = std::max_element(x.begin(),x.end(),[] (const std::pair<char,int>& a, const std::pair<char,int>& b)->bool{ return a.second < b.second; } );
    std::cout << best->first << " , " << best->second << "\n";
}

Solution 3:

You never changed currentMax in your code.

map<int,unsigned> frequencyCount;
for(size_t i = 0; i < v.size(); ++i)
    frequencyCount[v[i]]++;

unsigned currentMax = 0;
unsigned arg_max = 0;
for(auto it = frequencyCount.cbegin(); it != frequencyCount.cend(); ++it ) }
    if (it ->second > currentMax) {
        arg_max = it->first;
        currentMax = it->second;
    }
}
cout << "Value " << arg_max << " occurs " << currentMax << " times " << endl;

Another way to find the mode is to sort the vector and loop through it once, keeping track of the indices where the values change.