Simple quiz program problem

I'm extremely new to c++.

I've been reading the tutorials and decided to write my own little program

I want the program to ask a couple of questions, and based on your answers, output your score as a percentage.

I was able to write part of it, but I don't know how to complete it.

I can't figure out how to get the program to see how many you got right, then calculate your score.

Such as, if I got two right, I want it to say "your score is 66%" Or if I just got one right, "your score is 33%"

How would I go about doing this?

Heres the code I have so far.

Code:

---

#include<iostream>
using namespace std;

int main ()
{
    int add;
    int sub;
    int div;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;

if (add == 4 && sub == 0 && div == 5)
{
  cout << "Your score is 100%! \n ";
  }
  else
  {
      cout << "You got one wrong :( \n";
  }
system("Pause");
return 0;
}

---

first off if you're going to do it this way, you will have to satisfy the rest of the possible answers in your if statements. You have one for your 100% answer. Think of the other scenarios that you have. and give that a try

Create a counter in lieu of the numerous if statements. IE., int counter=0; Each time an answer is correct, do ++counter; At the end of your Q & A, compare the counter count to the number of questions asked.

So, if you asked 3 and your counter say you've answered 1 correct, well, do the math. There's an operand that can compute the percentage. ;)

Quote:

---

Originally Posted by todouble22

first off if you're going to do it this way, you will have to satisfy the rest of the possible answers in your if statements. You have one for your 100% answer. Think of the other scenarios that you have. and give that a try

---

Ah, thanks, something like this you mean?

Code:

---

#include<iostream>
using namespace std;

int main ()
{
    int add;
    int sub;
    int div;
    int counter=0

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;

if (add == 4 && sub == 0 && div == 5)
{
  cout << "Your score is 100%!\n" ;
  }
else
{
    if (add == 4 && sub == 0)
      {
      cout << "Your score is 66%! \n";
      }
    else
      {
          if (add == 4)
          {
            cout << "Your score is 33%! \n";
            }
          else
          {
              if (add == 4 && div == 5)
              {
                cout << "Your score is 66%! \n";
                }
              else
              {
                    if (div == 5)
                    {
                      cout << "Your score is 33%! \n";
                      }
                    else
                    {
                        if (sub == 0)
          {
            cout << "Your score is 33%! \n";
            }
          else
          {
              if (sub == 0 && div == 5)
              {
                cout << "Your score is 66%! \n";
                }
                else
                {
                        cout << "Your score is 0%!\n";
                        }
                    }
              }
          }
    }
system("Pause");
return 0;
}
}
}

---

Quote:

---

Originally Posted by Oldman47

Create a counter in lieu of the numerous if statements. IE., int counter=0; Each time an answer is correct, do ++counter; At the end of your Q & A, compare the counter count to the number of questions asked.

So, if you asked 3 and your counter say you've answered 1 correct, well, do the math. There's an operand that can compute the percentage. ;)

---

Sorry for my nubness, I don't understand what you mean, do you mean something like this?

Code:

---

#include<iostream>
using namespace std;

int main ()
{
    int add;
    int sub;
    int div;
    int counter = 0;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;
   
if (add == 4)
{
    ++counter;
  }
else
{
    if (sub == 0)
      {
      ++counter;
      }
    else
      {
          if (add == 4)
          {
            ++counter;
            }
          else
          {
              if (div == 5)
              {
                ++counter;
                }
                else
                {
                        cout << "Your score is 0%!\n";
                        }
                    }
              }
          }

system("Pause");
return 0;
}

---

Only I don't know how to use the counter to output the percentage though.

Well, I was thinking more along the lines of what's below. Before doing a board search, try to figure out percentages on your own. ;)

Code:

---

int num_correct=0; //initialize a counter for correct answers
int answer;

 void Check_Qs(int a)  //function to check user response against answers
  {
    int add_return = 4;  //correct addition total
    int sub_return = 0;  //correct subtraction total
    int div_return = 5;  //correct division answer


  if(add_return==a || sub_return==a || div_return == a){  //condense all if/else statements
    ++num_correct;          //if corrrect, score one for the user
    cout<<"correct! \n";
    }
    else {
      cout<<"wrong! \n" ;  //if wrong,  no score added - inform user he/she is wrong
    }
  }



int main()
 {
    cout << "Whats 2 + 2? ";
    cin >>answer;
    Check_Qs(answer);  //call function.  compare user answer against add_return value
   
        cout << "Whats 2 - 2? ";
        cin >> answer;
        Check_Qs(answer); //call function. compare user answer against sub_return value
   
    cout << "Whats 20 / 4? ";
    cin >> answer;
    Check_Qs(answer);  // call function. compare user answer against div_return value
   
    cin.ignore();  //ignore input so program doesn't close immediately
    cin.get();
      return 0;
    }

---

oldman, the user paulb39 is a noob. you're giving him examples of functions and calling to them within your main method.. do you seriously think that will get what you're doing without even knowing what they are?

I'm not attempting to discredit your assistance to the user but in the beginning it can be a bit daunting and at least as i've noticed its best to fully explain

Quote:

---

Originally Posted by Oldman47

Well, I was thinking more along the lines of what's below. Before doing a board search, try to figure out percentages on your own. ;)

-snip-

---

Thanks, tho any chance can you comment that code, I can't understand any of it ;(
I'm really new to c++, I'd like to learn what your thought process was when you wrote that.

Commented. Basically, I was trying to do away with most of your if/else statements and the function was created for that reason, along with keeping the code compact.

Quote:

---

Originally Posted by Oldman47

Commented. Basically, I was trying to do away with most of your if/else statements and the function was created for that reason, along with keeping the code compact.

---

Thanks, tho that is like my original code, doesn't give a percentage based on how many you got right.

Quote:

---

Originally Posted by paulb39

Thanks, tho that is like my original code, doesn't give a percentage based on how many you got right.

---

do you want a method to calculate percentage or just display in this example? as it stands now:

Code:

---

#include "stdafx.h"
#include<iostream>
using namespace std;

int num_correct=0; //initialize a counter for correct answers



 void Check_Qs(int a)  //function to check user response against answers
  {
    int add_return = 4;  //correct addition total
    int sub_return = 0;  //correct subtraction total
    int div_return = 5;  //correct division answer
 


  if(add_return==a || sub_return==a || div_return == a){  //condense all if/else statements
    ++num_correct;          //if corrrect, score one for the user, this will increment the number for each correct answer
    cout<<"correct! \n";
    }
    else {
      cout<<"wrong! \n" ;  //if wrong,  no score added - inform user he/she is wrong
    }
 }
 
 



 int main(){
        int answer;



    cout << "Whats 2 + 2? ";
    cin >>answer;
    Check_Qs(answer);  //call function.  compare user answer against add_return value
   
        cout << "Whats 2 - 2? ";
        cin >> answer;
        Check_Qs(answer); //call function. compare user answer against sub_return value
   
    cout << "Whats 20 / 4? ";
    cin >> answer;
    Check_Qs(answer);  // call function. compare user answer against div_return value

        //this portion below will use the number derived from the counter and write out
        //the percentage based on answers correct
        if (num_correct == 3){
        cout <<"you got " <<num_correct << " out of 3 correct which is 100%"<<endl;
        }
        else if (num_correct == 2){
        cout <<"you got " <<num_correct << " out of 3 correct which is 66%"<<endl;
        }
        else if (num_correct == 1){
        cout <<"you got " <<num_correct << " out of 3 correct which is 33%"<<endl;
        }
return 0;
}

---

You can eliminate those if/else statements with a little math, bub. ;)

Code:

---

    int percentage=num_correct*100/3;
    cout<<"You've scored "<<percentage<<" on this quiz";

---

Also, the function I wrote isn't foolproof. If for instance, you give the answer 0 for what is 2+2 the function would still return correct. It wasn't well thought out, just something I typed in on the fly. I also just typed in your percentage code, so you'd have too verify accuracy.

Quote:

---

Originally Posted by todouble22

do you want a method to calculate percentage or just display in this example? as it stands now:

Code:

---

#include "stdafx.h"
#include<iostream>
using namespace std;

int num_correct=0; //initialize a counter for correct answers



 void Check_Qs(int a)  //function to check user response against answers
  {
    int add_return = 4;  //correct addition total
    int sub_return = 0;  //correct subtraction total
    int div_return = 5;  //correct division answer
 


  if(add_return==a || sub_return==a || div_return == a){  //condense all if/else statements
    ++num_correct;          //if corrrect, score one for the user, this will increment the number for each correct answer
    cout<<"correct! \n";
    }
    else {
      cout<<"wrong! \n" ;  //if wrong,  no score added - inform user he/she is wrong
    }
 }
 
 



 int main(){
        int answer;



    cout << "Whats 2 + 2? ";
    cin >>answer;
    Check_Qs(answer);  //call function.  compare user answer against add_return value
   
        cout << "Whats 2 - 2? ";
        cin >> answer;
        Check_Qs(answer); //call function. compare user answer against sub_return value
   
    cout << "Whats 20 / 4? ";
    cin >> answer;
    Check_Qs(answer);  // call function. compare user answer against div_return value

        //this portion below will use the number derived from the counter and write out
        //the percentage based on answers correct
        if (num_correct == 3){
        cout <<"you got " <<num_correct << " out of 3 correct which is 100%"<<endl;
        }
        else if (num_correct == 2){
        cout <<"you got " <<num_correct << " out of 3 correct which is 66%"<<endl;
        }
        else if (num_correct == 1){
        cout <<"you got " <<num_correct << " out of 3 correct which is 33%"<<endl;
        }
return 0;
}

---

---

Calculate it, not just display

I took a different approach, made it add to "incorrect" and "correct" then in end divide "correct" by "total"

It compiles fine, but for some reason ,it always says "you scored 0 percent"

Any ideas?

Code:

---

#include<iostream>
using namespace std;

int main ()
{
    int add;
    int sub;
    int div;
    int correct =0;
    int incorrect =0;
    int total =3;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;
    std::cout<< "You scored, " << correct / total << " percent\n";

if (add == 4)
{
  ++correct;
  }
else
{
    if (add != 4)
      {
      ++incorrect;
      }
    else
      {
          if (sub == 0)
          {
            ++correct;
            }
          else
          {
              if (sub != 0)
              {
                ++incorrect;
                }
              else
              {
                    if (div == 5)
                    {
                      ++correct;
                      }
                    else
                    {
                        if (div != 5)
          {
            ++correct;
            }
                                  }

                    }
              }
          }
    }
system("Pause");
return 0;
}

---

Quote:

---

Originally Posted by paulb39

It compiles fine, but for some reason ,it always says "you scored 0 percent"

---

That is due to integer division. You can cast one of the two operands to float or double as you divide.

Quote:

---

Originally Posted by laserlight

That is due to integer division. You can cast one of the two operands to float or double as you divide.

---

*head explodes*

What do you mean?

I fixed it by adding

cout<< "You scored, " << correct / total << " percent\n";

to the end, but now it always outputs "you scored 45 percent"

Code:

---

#include<iostream>
#include<string>
using namespace std;

int main ()
{
    int add;
    int sub;
    int div;
    int correct;
    int incorrect =0;
    int total =3;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;


if (add == 4)
{
  ++correct;
  }
else
{
    if (add != 4)
      {
      ++incorrect;
      }
    else
      {
          if (sub == 0)
          {
            ++correct;
            }
          else
          {
              if (sub != 0)
              {
                ++incorrect;
                }
              else
              {
                    if (div == 5)
                    {
                      ++correct;
                      }
                    else
                    {
                        if (div != 5)
          {
            ++correct;
            }
                                  }

                    }
              }
          }
    }
    {
    cout<< "You scored, " << correct / total << " percent\n";
}
system("Pause");
return 0;
}

---

Quote:

---

Originally Posted by paulb39

What do you mean?

---

Something like this:

Code:

---

cout << "You scored, " << static_cast<int>((correct * 100.0) / total) << " percent\n";

---

Before we continue, I suggest that you indent your code properly, e.g.,

Code:

---

#include<iostream>
#include<string>

using namespace std;

int main()
{
    int add;
    int sub;
    int div;
    int correct;
    int incorrect = 0;
    int total = 3;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;

    if (add == 4)
    {
        ++correct;
    }
    else
    {
        if (add != 4)
        {
            ++incorrect;
        }
        else
        {
            if (sub == 0)
            {
                ++correct;
            }
            else
            {
                if (sub != 0)
                {
                    ++incorrect;
                }
                else
                {
                    if (div == 5)
                    {
                        ++correct;
                    }
                    else
                    {
                        if (div != 5)
                        {
                            ++correct;
                        }
                    }
                }
            }
        }
    }

    {
        cout<< "You scored, " << correct / total << " percent\n";
    }
    system("Pause");
    return 0;
}

---

Note that those nested if-else statements would more typically be written as:

Code:

---

if (add == 4)
{
    ++correct;
}
else if (add != 4)
{
    ++incorrect;
}
else if (sub == 0)
{
    ++correct;
}
else if (sub != 0)
{
    ++incorrect;
}
else if (div == 5)
{
    ++correct;
}
else if (div != 5)
{
    ++correct;
}

---

Either way, with indentation, it is clear that the quiz taker can only get at most 1 question reported as correct. Even if he/she got the other questions correct, they would never be checked for correctness. Likewise, the quiz taker can get at most 1 question reported as incorrect.

Also, one more issue.

Code:

---

int correct;
...
++correct;

---

You should initialize the variable before using it.

Quote:

---

Originally Posted by _Mike

Also, one more issue.

Code:

---

int correct;
...
++correct;

---

You should initialize the variable before using it.

---

This initializes it right?

Code:

---

int correct;
    int incorrect;
    int total;
    correct = 0;
    incorrect = 0;
    total = 3;

---

Quote:

---

Originally Posted by laserlight

Either way, with indentation, it is clear that the quiz taker can only get at most 1 question reported as correct. Even if he/she got the other questions correct, they would never be checked for correctness. Likewise, the quiz taker can get at most 1 question reported as incorrect.

---

I don't understand why though.

The way I have it now, it always outputs "your score is 33 percent"

Code:

---

#include<iostream>
#include<string>

using namespace std;

int main()
{
    int add;
    int sub;
    int div;
    int correct;
    int incorrect;
    int total;
    correct = 0;
    incorrect = 0;
    total = 3;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;

    if (add == 4)
    {
    ++correct;
    }
    else if (add != 4)
    {
    ++incorrect;
    }
    else if (sub == 0)
    {
    ++correct;
    }
    else if (sub != 0)
    {
    ++incorrect;
    }
    else if (div == 5)
    {
    ++correct;
    }
    else if (div != 5)
    {
    ++correct;
    }
    {
        cout << "You scored, " << static_cast<int>((correct * 100.0) / total) << " percent\n";
    }
    system("Pause");
    return 0;
}

---

Quote:

---

Originally Posted by paulb39

This initializes it right?

---

No, you should initialise it to 0:

Code:

---

int correct = 0;

---

Quote:

---

Originally Posted by paulb39

I don't understand why though.

---

Trace the logic. For example, suppose that add == 4. Then ++correct. But the else branch will not be followed, hence the next thing that happens is that the result is printed. But suppose that add != 4. You know that add == 4 will evaluate to false, hence the else branch will be followed. Now, add != 4 evaluates to true, hence ++incorrect. But now the else branch here will not be followed, hence the next thing that happens is that the result is printed. Since either add == 4 or add != 4, there is no way that sub == 0 will ever get checked.

Rather, you should have three separate if-else statements, each handling a question independently of the others.

Quote:

---

Originally Posted by laserlight

Rather, you should have three separate if-else statements, each handling a question independently of the others.

---

Woot, thank you, working now

Code:

---

#include<iostream>
#include<string>

using namespace std;

int main()
{
    int add;
    int sub;
    int div;
    int correct = 0;
    int incorrect = 0;
    int total = 3;

    cout << "Whats 2 + 2? ";
    cin >> add;
    cout << "Whats 2 - 2? ";
    cin >> sub;
    cout << "Whats 20 / 4? ";
    cin >> div;

    if (add == 4)
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (div == 5)
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (sub == 0)
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    {
        cout << "You scored, " << static_cast<int>((correct * 100.0) / total) << " percent\n";
    }
    system("Pause");
    return 0;
}

---

One question, for

Code:

---

cout << "You scored, " << static_cast<int>((correct * 100.0) / total) << " percent\n";

---

Could you explain what it means? I don't understand what the "static_cast<int>" part is for, and why does correct need two parentheses in front of if instead of one?

Quote:

---

Originally Posted by paulb39

I don't understand what the "static_cast<int>" part is for

---

From what I see, you want to output an int rather than a double, so this a type cast to coerce the double to int. It truncates the double in the process (i.e., the portion after the decimal point is "chopped off"), but other than that it probably does what you want.

Quote:

---

Originally Posted by paulb39

and why does correct need two parentheses in front of if instead of one?

---

Because I chose to use parentheses to group (correct * 100.0). This is actually unnecessary.

Quote:

---

Originally Posted by laserlight

From what I see, you want to output an int rather than a double, so this a type cast to coerce the double to int. It truncates the double in the process (i.e., the portion after the decimal point is "chopped off"), but other than that it probably does what you want.


Because I chose to use parentheses to group (correct * 100.0). This is actually unnecessary.

---

Thanks.

Wrote another program, does same sort of thing but I tried to make it a little long/ more complicated.

Got it to work in my first try, which is pretty awesome, but it doesn't calculate the percent correct, it always says "you scored 25 percent"

I'm guessing its because I have int and char variables.

Any ideas?

Code:

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#include<iostream>
#include<string>

using namespace std;

int main()
{
    int mole;
    char gas_law[7];
    int num;
    char place_p[11];
    char place_v[1];
    char place_n[1];
    char place_r[1];
    char place_t[1];
    int correct = 0;
    int incorrect = 0;
    int total = 8;

    cout << "Write a number 1 - 10 ";
    cin >> num;
    cout << "What is the 16th letter in the alphabet? ";
    cin >> place_p;
    cout << "What is the 22nd letter in the alphabet? ";
    cin >> place_v;
    cout << "What is the 14th letter in the alphabet? ";
    cin >> place_n;
    cout << "What is the 18th letter in the alphabet? ";
    cin >> place_r;
    cout << "What is the 20th letter in the alphabet? ";
    cin >> place_t;
    cout << "What is the ideal gas law? (use all lower case) Hint: ^^ " ;
    cin >> gas_law;
    cout << "How many moles are in 80 grams of Calcium? Hint: calcium is Ca ";
    cin >> mole;

    if (gas_law == "pv=nrt")
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (place_p == "p")
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (place_v == "v")
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (place_n == "n")
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (place_r == "r")
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (place_t == "t")
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (mole == 2)
    {
    ++correct;
    }
    else
    {
    ++incorrect;
    }
    if (num == 3)
    {
    ++correct;
    cout << "You guessed the number correctly! Aren't you a genius...\n";
    }
    else if (num < 3)
    {
    ++incorrect;
    cout << "You should of gussed higher for the number!\n";
    }
    else if (num > 3)
    {
    cout << "You should of guessed lower for the number!\n";
    }
    {
        cout << "You scored, " << static_cast<int>((correct * 100.0) / total) << " percent\n";
    }
    system("Pause");
    return 0;
}

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