Random Number Generator

[jgirl2412]

I created this program for a class assignment and it works fine but I noticed that sometimes it will return 2 of the same numbers in the same run. Is there a way to make sure that it returns unique integers each run?

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

//function prototypes
void displayArray(int numbers[], int numElements);
int getHighest(int numbers[], int numElements);

int main()
{
//declare array
int randNums[6] = {0};
int sub = 0;
int temp = 0;
int maxSub = 5;
int lastSwap = 0;
char swap = 'Y';

//initialize random number generator
srand(static_cast<int>(time(0)));
//assign random integers from 1 through 54 to the array
for (int sub = 0; sub < 6; sub += 1)
randNums[sub] = 1 + rand() % (54 - 1 + 1);
//end for

while (swap == 'Y')
{
swap = 'N'; //assume no swaps are necessary

sub = 0; //begin comapring with first
//array element

//compare adjacent array elements to determine
//whether a swap is necessary
while (sub < maxSub)
{
if (randNums[sub] > randNums[sub + 1])
{
//a swap is necessary
temp = randNums[sub];
randNums[sub] = randNums[sub + 1];
randNums[sub + 1] = temp;
swap = 'Y';
lastSwap = sub;
} //end if
sub+=1; //increment subscript
} //end while

maxSub = lastSwap; //reset maximum subscript
} //end while

//display array
displayArray(randNums, 6);

//display the highest number in the array
cout << endl << "Highest number: " << getHighest(randNums, 6) << endl;

return 0;
} //end of main

//*****function definitions*****
void displayArray(int numbers[], int numElements)
{
for (int sub = 0; sub < numElements; sub += 1)
cout << numbers[sub] << endl;
//end for
} //end of displayArray function

int getHighest(int numbers[], int numElements)
{
//assign first element'e value to the highest variable
int high = numbers[0];

//begin the search with the second element
int x = 1;

//search for highest number
while (x < numElements)
{
if (numbers[x] > high)
high = numbers[x];
//end if
x += 1;
} //end while

return high;
} //end of getHighest function

[soultrip]

just keep track of the numbers that have already been produced. Then if a number is generated twice just throw that value away and run the generator again until you get a unique number.

[Disch]

An alternative is to put all the possible numbers in an array (only one number each, easily done with a for loop), then call std::random_shuffle to shuffle the array contents around.

Then you can pick the first handful of values and you can be sure that they will all be unique.

[jgirl2412]

Thanks, I'll give that a try.

[creekist]

I think this will generation better random numbers:

#include<iostream>
#include<cstdlib>
#include<time.h>
using namespace std;

int main(){
	srand(time(0));
	cout << rand() << endl;
	return 0;}

[Disch]

That's what he's doing, creekist. The problem is he needs numbers within a certain range, and the numbers he picks can't be duplicates.