Need Help Generating Random Numbers In C++

This is a discussion on Need Help Generating Random Numbers In C++ within the C++ Programming forums, part of the General Programming Boards category; Okay dudes, I have this program and when I run it I need it to generater random numbers, but I ...

  1. #1
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    Need Help Generating Random Numbers In C++

    Okay dudes, I have this program and when I run it I need it to generater random numbers, but I can't seem to figure out how to use the srand() thing to do it. Thank for the help in advance.

    Code:
    #include <iostream>
    #include <cstdlib>
    using namespace std;
    
    int main()
    {
    	
    	bool TrueFalse1, TrueFalse2, TrueFalse3, TrueFalse4, TrueFalse5;
    	long int xNumber = 1 + rand() % 50,
    		yNumber = 1 + rand() % 50,
    		A = 1 + rand() % 50,
    		B = 1 + rand() % 50,
    		C = 1 + rand() % 50,
    		result1, result2, result3, result4, result5,
    		answer1, answer2, answer3,answer4,answer5,
    		result,
    		total,
    		x = xNumber,
    		y = yNumber;
    
    	cout<<"Solve the following expression where x = "<<xNumber << " and y = "<<yNumber<<endl;
    	cout<<A<<" x + "<<B<<" y + "<<C<<endl;
    	cout<<"Write your result:\n";
    	cin>> result1; 
    	answer1 = (A * x) + (B * y) + C;
    	
    	
    	if (result1 == answer1)
    		cout<<"Your answer is correct\n";
    	else
    		cout<<"Your answer is wrong. The correct answer is "<<answer1<<endl;
    	TrueFalse1 = (result1 == answer1);
    
    
    
    	
    	cout<<"Solve the following expression where x = "<<xNumber<<" and y = "<<yNumber<<endl;
    	cout<<A<<" x + "<<B<<" y + "<<C<<endl;
    	cout<<"Write your result:\n";
    	cin>> result2;
    	answer2 = (A * x) + (B * y) + C;
    	
    
    	if (result2 == answer2)
    		cout<<"Your answer is correct\n";
    	else
    		cout<<"Your answer is wrong. The correct answer is "<<answer2<<endl;
    	TrueFalse2 = (result2 == answer2);
    
    	
    	cout<<"Solve the following expression where x = "<<xNumber<<" and y = "<<yNumber<<endl;
    	cout<<A<<" x + "<<B<<" y + "<<C<<endl;
    	cout<<"Write your result:\n";
    	cin>> result3;
    	answer3 = (A * x) + (B * y) + C;
    	
    
    	if (result3 == answer3)
    		cout<<"Your answer is correct\n";
    	else
    		cout<<"Your answer is wrong. The correct answer is "<<answer3<<endl;
    	TrueFalse3 = (result3 == answer3);
    
    	
    	cout<<"Solve the following expression where x = "<<xNumber<<" and y = "<<yNumber<<endl;
    	cout<<A<<" x + "<<B<<" y + "<<C<<endl;
    	cout<<"Write your result:\n";
    	cin>> result4;
    	answer4 = (A * x) + (B * y) + C;
    
    
    	if (result4 == answer4)
    		cout<<"Your answer is correct\n";
    	else
    		cout<<"Your answer is wrong. The correct answer is "<<answer4<<endl;
    	TrueFalse4 = (result4 == answer4);
    	
    
    	
    	cout<<"Solve the following expression where x = "<<xNumber<<" and y = "<<yNumber<<endl;
    	cout<<A<<" x + "<<B<<" y + "<<C<<endl;
    	cout<<"Write your result:\n";
    	cin>> result5;
    	answer5 = (A * x) + (B * y) + C;
    
    
    	if (result5 == answer5)
    		cout<<"Your answer is correct\n";
    	else
    		cout<<"Your answer is wrong. The correct answer is "<<answer5<<endl;
    	TrueFalse5 = (result5 == answer5);
    
    	total = TrueFalse1 + TrueFalse2 + TrueFalse3 + TrueFalse4 + TrueFalse5;
    	cout<< "You answered "<<total<<" correctly.\n";
    	return 0;
    
    }

  2. #2
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    Code:
    #include <time.h>
    #include <stdlib.h>
    
    srand(time(NULL));
    Call it once at the begine of your program.
    These basic questions are covered in the FAQ

  3. #3
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    Thanks for the advice, I look into the faq, but I could not solve the problem (I got the same values every time I ran the programm). I am a real Newbie to programming in C++. Could someone please help me a litter further.

  4. #4
    C++ Witch laserlight's Avatar
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    Put your current program aside, and come up with the smallest and simplest program that has this problem. An example would be a program that prints just 5 pseudo-random numbers. Run it a few times, and see if you still get the same values every time the program is run.
    C + C++ Compiler: MinGW port of GCC
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  5. #5
    and the hat of wrongness Salem's Avatar
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    Post your code showing your call to srand();
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  6. #6
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    I don't know where to put the srand(), so it does not show the same numbers everytime. Here is the simple random number program, but I don't know how to make it so a user does not have to enter a seed number in order of it to generate random number and how can a generate a random number to a defined variable that equals a random number.

    Code:
    #include <iostream>
    #include <cstdlib>
    using namespace std;
    
    int main()
    {
    	unsigned seed,y;
    	cout<< "Enter seed\n";
    	cin >> seed;
    	srand(seed);
    
    
    	y=1+rand()%50;
    	cout<<y<<endl;
    	return 0;
    
    }

  7. #7
    Frequently Quite Prolix dwks's Avatar
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    Try this:

    Code:
    #include <iostream>
    #include <cstdlib>
    #include <ctime>
    
    int main() {
        srand(time(0));
    
        cout << (rand() % 100) << endl;
    
        return 0;
    }
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  8. #8
    and the hat of wrongness Salem's Avatar
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    > I don't know where to put the srand()
    The FAQ seemed pretty clear to me!

    "If you want to get different random numbers each time you run your program, you will also need to use the srand() function"

    "To get different random number set, pass a different seed. The most common way to achieve this is by calling the time() function and passing its result to srand()"

    And there's an example right there, showing
    srand(time(NULL));
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  9. #9
    Dump Truck Internet valis's Avatar
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    you also might try a different function set, rand isn't exactly the best function out there.

  10. #10
    Frequently Quite Prolix dwks's Avatar
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    What's a better one?
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
    Unofficial Wiki FAQ: cpwiki.sf.net

    My website: http://dwks.theprogrammingsite.com/
    Projects: codeform, xuni, atlantis, nort, etc.

  11. #11
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    Thanks guys I got it to work!

  12. #12
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    Be sure to cast time(0) to what ever type srand takes.

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