#include <cstdlib>
#include <ctime>
#include <iostream>
#include <vector>
 
// nValues is the number of unique values to generate.
// vals points to an array large enough to hold nValues numbers.
// min is the smallest number in the range to generate numbers for.
// max is the largest number in the range to generate numbers for.
// IMPORTANT:  max-min cannot exceed 255.
void generateUniqueRandomValues(unsigned nValues, unsigned* vals, unsigned min, unsigned max)
{
    using std::swap;
    using std::rand;
 
    const unsigned maxElements = 256 ;                  // some arbitrary value.
    unsigned values[maxElements];
 
    const unsigned valuesSize = max - min + 1;          // the number of elements of the values array which we will use.
 
    for (unsigned i = 0; i < valuesSize; ++i)           // fill values with numbers from min to max.
        values[i] = min + i;
 
    for (unsigned i = 0; i < nValues; ++i)
    {
        const unsigned valuesLeft = valuesSize - i;
 
        const unsigned index = rand() % valuesLeft;     // pick a random index for an unused value.
        vals[i] = values[index];                        // store the value in the user-supplied array.
 
        swap(values[index], values[valuesLeft-1]);      // swap the used value with the last unused value.
    }
}
 
int main()
{
    using namespace std;
 
    srand(time(0));
 
    const unsigned nVals = 7;
    const unsigned minVal = 1;
    const unsigned maxVal = 50;
 
    unsigned randValues[nVals];
    generateUniqueRandomValues(nVals, randValues, minVal, maxVal);
 
 
    for (unsigned i = 0; i < nVals; ++i)
        cout << "#" << i+1 << ": " << randValues[i] << '\n' ;
}

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