Random Number Generation Range Issues

Mr D (79)
Coding a guessing game with difficulties. The secret number can range anyone from 1 to 1000000, but when generating the number for anything over about 10000, I always get roughly the same number. Why is it the larger ranges all produce roughly the same number? ( Around 15,000 ).

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#include <iostream>
#include <fstream>
#include <windows.h>
#include <stdexcept>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>


struct Difficulty_Struct {
    std::string name;
    int lower_limit;
    int upper_limit;
};

static const int MAX_DIFF = 6;
Difficulty_Struct Difficulties[MAX_DIFF];

int selected_difficulty;
int secret_number;

void load_from_file();
void game_initializer();
int get_input();
void difficulty_selection();
void generate_secret_number();






int main()
{
    game_initializer();
    difficulty_selection();
    generate_secret_number();
    return 0;
}



void load_from_file()
{
    std::ifstream file("GameData/Difficulty.txt");
    if ( file.is_open() )
    {
        int counter = 0;
        while ( file >> Difficulties[counter].name >> Difficulties[counter].lower_limit >> Difficulties[counter].upper_limit )
        {
            if ( counter >= MAX_DIFF - 1 )
            {
                break;
            }

            counter++;
        }

        file.close();
    }
    else
    {
        throw std::invalid_argument("Could not locate GameData/Difficulty.txt.");
    }
}

void game_initializer()
{
    srand (time(NULL));
    system("Color 1e");
    SetConsoleTitle("Number guess 1.0");
    std::cout << "Number Guess 1.0 by Max Daniels" << std::endl;
    std::cout << "-------------------------------" << std::endl;
    std::cout << "Please select a difficulty by typing the appropriate number!\n\n" << std::endl;
    load_from_file();
    for ( int x = 0; x < MAX_DIFF; x++ )
    {
        std::cout << (x + 1) << ") ";
        std::cout << Difficulties[x].name << " ";
        std::cout << Difficulties[x].lower_limit;
        std::cout << "-" << Difficulties[x].upper_limit << std::endl;
    }

}

int get_input()
{
    std::cout << std::endl;
    int choice;
    bool validInput = false;
    do {
        std::cout << ">";
        std::cin >> choice;

        if ( std::cin.fail() )
        {
            std::cin.clear();
            std::cin.ignore(100, '\n');
            std::cout << "Please input a valid number." << std::endl;
        }
        else
        {
            validInput = true;
        }
    }
    while ( !validInput );
    return choice;
}

void difficulty_selection()
{
    int choice = 0;
    enum {DifficultyOne = 1, DifficultyTwo, DifficultyThree, DifficultyFour, DifficultyFive, DifficultySix};
    while ( choice <= 0 || choice > 6 )
    {
        choice = get_input();

        switch ( choice )
        {
            case DifficultyOne: selected_difficulty = DifficultyOne - 1;
                break;
            case DifficultyTwo: selected_difficulty = DifficultyTwo - 1;
                break;
            case DifficultyThree: selected_difficulty = DifficultyThree - 1;
                break;
            case DifficultyFour: selected_difficulty = DifficultyFour - 1;
                break;
            case DifficultyFive: selected_difficulty = DifficultyFive - 1;
                break;
            case DifficultySix: selected_difficulty = DifficultySix - 1;
                break;
            default: std::cout << "Invalid selection, please select between 1-6." << std::endl;
                     choice = 0;
        }
    }
}

void generate_secret_number()
{
    secret_number = rand() % Difficulties[selected_difficulty].upper_limit + Difficulties[selected_difficulty].lower_limit;
    //Code for Testing
    std::cout << secret_number << std::endl;
}
Mr D (79)
The issue lies in the function on line 138. The random number generator is the first thing that starts in the program, line 69.
Mr D (79)
Is there an issue with using Rand() for large numbers?
Jims (25)
yes I belive there is a problem with Rand and big numbers. If you have a compiler that can handle c++11 then you should use one of the new random number generators.

If you don't have c++11 then just use rand to generate three or four smaller numbers and multiply them together.
CodeWriter (286)
Duthomhas (13200)
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