Since you didn't provide any code, I decided to try it myself. Here's what I came up with. Maybe it'll give you some hints as to what you did wrong.

#include <string>
#include <vector>
#include <fstream>
#include <iostream>
#include <algorithm>
#include <sstream>

auto split(std::string str, char delimiter)
{
    std::vector<std::string> output;
    std::stringstream ss(str);

    for(std::string str; std::getline(ss, str, delimiter);)
        output.push_back(str);

    return output;
}

int main()
{
    std::ifstream in("textfile");
    std::string content;
    std::vector<std::string> vec_content;
    std::vector<int> converted_content; //Converted from string to int

    for(std::string line; std::getline(in, line);)
    {
        content.append(line);
        content.append(" ");
    }

    vec_content = split(content, ' ');

    for(auto it = std::begin(vec_content); it != std::end(vec_content); it++)
        converted_content.push_back(std::stoi(*it));

    std::cout << "Max value: " << *std::max_element(std::begin(converted_content), std::end(converted_content)) << std::endl;
    std::cout << "Min value: " << *std::min_element(std::begin(converted_content), std::end(converted_content)) << std::endl;

    std::cout << "Odd numbers: ";   
    for(auto it = std::begin(converted_content); it != std::end(converted_content); it++)
    {
        if(*it%2)
            std::cout << *it << " ";
    }

    std::cout << std::endl << "Even numbers: ";
    for(auto it = std::begin(converted_content); it != std::end(converted_content); it++)
    {
        if(!(*it%2))
            std::cout << *it << " ";
    }

    std::cout << std::endl;

    return 0;
}

Example text file:

1 2 3 4 5
-92 1034 90000 62
-1 -2 -85 8

Output:

Max value: 90000
Min value: -92
Odd numbers: 1 3 5 -1 -85 
Even numbers: 2 4 -92 1034 90000 62 -2 8