First Non-repeated Character (CodeEval)

first_nrc.cpp

/* First Non-repeated Character Moderate Challenge on CodeEval */
/* Comiple this with the -std=c++11 flag to prevent warnings */
#include <iostream>
#include <fstream>
#include <string>
#include <map>

struct Double 
{
        int val[2]; // { count, order }
};

char get_letter(std::map<char, Double> letter_map, int string_length) 
/* The list part of the map contains <count, order-found> */
{
    char result;
    int minimum = string_length;

    for (std::map<char, Double>::iterator it = letter_map.begin(); it != letter_map.end(); ++it) 
    {

        if (it->second.val[0] < 2 && it->second.val[1] < minimum) 
        {
            result = it->first;
            minimum = (minimum > it->second.val[1]) ? it->second.val[1] : minimum;
        }
    }
    return result;
}

int main(int argc, char *argv[]) 
{
    Double info; 
    std::ifstream stream(argv[1]);
    std::string line;
    std::map<char, Double> characters; // the map
    
    while (getline(stream, line)) 
    {
        // Do something with the line
        int length = line.length();
        int count = 1; 

        for (int i = 0; i < length; i++) 
        {
            
        	if (characters.count(line[i]) == 0) 
        	{
                
        		info = {1,i};
        		characters.insert(std::pair<char, Double>(line[i], info));
        	} else
        	{
                	count +=1;
                	std::map<char, Double>::iterator it = characters.find(line[i]);
                
                	if (it != characters.end()) 
                	{
                    		it->second.val[0] = count;
                	}
        	}
    	}
        std::cout<<get_letter(characters, length)<<std::endl;
        characters.clear();
    }
    return 0;
}