/*
Challenge 195

Task 2: Most Frequent Even
Submitted by: Mohammad S Anwar
You are given a list of numbers, @list.

Write a script to find most frequent even numbers in the list. In case you
get more than one even numbers then return the smallest even integer. For all
other case, return -1.

Example 1
Input: @list = (1,1,2,6,2)
Output: 2 as there are only 2 even numbers 2 and 6 and of those 2 appears
the most.
Example 2
Input: @list = (1,3,5,7)
Output: -1 since no even numbers found in the list
Example 3
Input: @list = (6,4,4,6,1)
Output: 4 since there are only two even numbers 4 and 6. They both appears
the equal number of times, so pick the smallest.
*/

#include <iostream>
#include <vector>

int most_freq_even(const std::vector<int>& nums) {
    std::vector<int> hist;
    for (size_t i=0; i<nums.size(); i++) {
        if (nums[i]>=static_cast<int>(hist.size()))
            hist.resize(nums[i]+1);
        hist[nums[i]]++;
    }
    int max_count=0;
    int max_even=-1;
    for (size_t i=0; i<hist.size(); i+=2) {
        if (hist[i]>max_count) {
            max_count=hist[i];
            max_even=i;
        }
    }
    return max_even;
}

int main(int argc, char* argv[]) {
    argv++; argc--;
    if (argc == 0) {
        std::cerr<<"usage: ch-2 nums..."<<std::endl;
        return EXIT_FAILURE;
    }

    std::vector<int> nums;
    for (int i = 0; i < argc; i++)
        nums.push_back(atoi(argv[i]));

    std::cout<<most_freq_even(nums)<<std::endl;
}