Generate a different random number each time, not the same one six times in a row.
Use case scenario
I likened Predictability's problem to a bag of six bits of paper, each with a value from 0 to 5 written on it. A piece of paper is drawn from the bag each time a new value is required. If the bag is empty, then the numbers are put back into the bag.
...from this, I can create an algorithm of sorts.
Algorithm
A bag is usually a Collection. I chose a bool[] (otherwise known as a boolean array, bit plane or bit map) to take the role of the bag.
The reason I chose a bool[] is because the index of each item is already the value of each piece of paper. If the papers required anything else written on them then I would have used a Dictionary<string, bool> in its place. The boolean value is used to keep track of whether the number has been drawn yet or not.
A counter called RemainingNumberCount is initialised to 5 that counts down as a random number is chosen. This saves us from having to count how many pieces of paper are left each time we wish to draw a new number.
To select the next random value I'm using a for..loop to scan through the bag of indexes, and a counter to count off when an index is false called NumberOfMoves.
NumberOfMoves is used to choose the next available number. NumberOfMoves is first set to be a random value between 0 and 5, because there are 0..5 available steps we can make through the bag. On the next iteration NumberOfMoves is set to be a random value between 0 and 4, because there are now 0..4 steps we can make through the bag. As the numbers are used, the available numbers reduce so we instead use rand() % (RemainingNumberCount + 1) to calculate the next value for NumberOfMoves.
When the NumberOfMoves counter reaches zero, the for..loop should as follows:
for..loop's index.false.for..loop.Code
The code for the above solution is as follows:
(put the following three blocks into the main .cpp file one after the other)
#include "stdafx.h"
#include <ctime>
#include <iostream>
#include <string>
class RandomBag {
public:
int Value = -1;
RandomBag() {
ResetBag();
}
void NextValue() {
int BagOfNumbersLength = sizeof(BagOfNumbers) / sizeof(*BagOfNumbers);
int NumberOfMoves = rand() % (RemainingNumberCount + 1);
for (int i = 0; i < BagOfNumbersLength; i++)
if (BagOfNumbers[i] == 0) {
NumberOfMoves--;
if (NumberOfMoves == -1)
{
Value = i;
BagOfNumbers[i] = 1;
break;
}
}
if (RemainingNumberCount == 0) {
RemainingNumberCount = 5;
ResetBag();
}
else
RemainingNumberCount--;
}
std::string ToString() {
return std::to_string(Value);
}
private:
bool BagOfNumbers[6];
int RemainingNumberCount;
int NumberOfMoves;
void ResetBag() {
RemainingNumberCount = 5;
NumberOfMoves = rand() % 6;
int BagOfNumbersLength = sizeof(BagOfNumbers) / sizeof(*BagOfNumbers);
for (int i = 0; i < BagOfNumbersLength; i++)
BagOfNumbers[i] = 0;
}
};
A Console class
I create this Console class because it makes it easy to redirect output.
Below in the code...
Console::WriteLine("The next value is " + randomBag.ToString());
...can be replaced by...
std::cout << "The next value is " + randomBag.ToString() << std::endl;
...and then this Console class can be deleted if desired.
class Console {
public:
static void WriteLine(std::string s) {
std::cout << s << std::endl;
}
};
Main method
Example usage as follows:
int main() {
srand((unsigned)time(0)); // Initialise random seed based on current time
RandomBag randomBag;
Console::WriteLine("First set of six...\n");
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
Console::WriteLine("\nSecond set of six...\n");
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
Console::WriteLine("\nThird set of six...\n");
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
randomBag.NextValue();
Console::WriteLine("The next value is " + randomBag.ToString());
Console::WriteLine("\nProcess complete.\n");
system("pause");
}
Example output
When I ran the program, I got the following output:
First set of six...
The next value is 2
The next value is 3
The next value is 4
The next value is 5
The next value is 0
The next value is 1
Second set of six...
The next value is 3
The next value is 4
The next value is 2
The next value is 0
The next value is 1
The next value is 5
Third set of six...
The next value is 4
The next value is 5
The next value is 2
The next value is 0
The next value is 3
The next value is 1
Process complete.
Press any key to continue . . .
Closing statement
This program was written using Visual Studio 2017, and I chose to make it a Visual C++ Windows Console Application project using .Net 4.6.1.
I'm not doing anything particularly special here, so the code should work on earlier versions of Visual Studio too.