Possible Duplicate:
Generating random integer from a range
I am trying to create a program where the computer guesses a number the user has in his/her mind. The only user input required is whether the guess was too high, too low, or correct. I'm having a problem generating a random number between two variables that store the min and max based on previous guesses. Here is my code:
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
int main()
{
srand(static_cast <unsigned int> (time(0)));
int compGuess = rand() % 100 +1; //Generates number between 1 - 100
int highestNumber = 100;
int lowestNumber = 1;
char ready;
char highLowSuccess;
bool success;
int tries = 0;
cout << "Please pick a number between 1 - 100. I will guess your number. Don't tell me what it is!\n\n";
do
{
cout << "Are you ready? (y/n)\n\n";
cin >> ready;
if (ready == 'y')
{
do
{
cout << "Is your number " << compGuess << "?\n\n";
cout << "High, Low or Success?";
++tries;
cin >> highLowSuccess; //User input telling the computer whether its too high, too low, or a success
if (highLowSuccess == 'h') //Executes code if number guessed was too high.
{
highestNumber = compGuess - 1; //Stores variable indicating the highest possible number based on user input
compGuess = rand() % highestNumber +1; //Generates a new random number between 1 and the new highest possible number
success = false;
}
else if (highLowSuccess == 'l') //Executes code if number guessed was too low.
{
lowestNumber = compGuess + 1;//Stores variable indicating the lowest possible number based on user input
compGuess = (rand() % highestNumber - lowestNumber + 1) + lowestNumber // <---- Not producing the desired result
success = false;
}
else if (highLowSuccess == 's') //Executes code if the computer's guess was correct.
{
cout << "I guessed your number! It only took me " << tries << " tries!";
success = true;
}
} while (success != true);
}
else
{
continue;
}
} while (ready != 'y');
return 0;
}
highestNumber is what the max should be and lowestNumber is what the min should be. I need an equation that lets me generate a random number while taking the highest and lowest possible numbers into account.
Forgive me if the answer is really simple, I'm a noob programmer. xD
This question is related to
c++
rand() % ((highestNumber - lowestNumber) + 1) + lowestNumber
If you have a C++11 compiler you can prepare yourself for the future by using c++'s pseudo random number faculties:
//make sure to include the random number generators and such
#include <random>
//the random device that will seed the generator
std::random_device seeder;
//then make a mersenne twister engine
std::mt19937 engine(seeder());
//then the easy part... the distribution
std::uniform_int_distribution<int> dist(min, max);
//then just generate the integer like this:
int compGuess = dist(engine);
That might be slightly easier to grasp, being you don't have to do anything involving modulos and crap... although it requires more code, it's always nice to know some new C++ stuff...
Hope this helps - Luke
Really fast, really easy:
srand(time(NULL)); // Seed the time
int finalNum = rand()%(max-min+1)+min; // Generate the number, assign to variable.
And that is it. However, this is biased towards the lower end, but if you are using C++ TR1/C++11 you can do it using the random
header to avoid that bias like so:
#include <random>
std::mt19937 rng(seed);
std::uniform_int_distribution<int> gen(min, max); // uniform, unbiased
int r = gen(rng);
But you can also remove the bias in normal C++ like this:
int rangeRandomAlg2 (int min, int max){
int n = max - min + 1;
int remainder = RAND_MAX % n;
int x;
do{
x = rand();
}while (x >= RAND_MAX - remainder);
return min + x % n;
}
and that was gotten from this post.
To generate a random number between min and max, use:
int randNum = rand()%(max-min + 1) + min;
(Includes max and min)
Source: Stackoverflow.com