Generating unique random characters and saving them in array

Question

I want to generate random numbers and save them in an array. that' all ! but here is the point, I want to avoid duplicating and not having a number two or more times in array.

my code :

#include <iostream>
#include <stdlib.h>
#include <time.h>

using namespace std;

int main()
{
    int k, temp;

    cin >> k;

    int sym[k];

    srand(time(NULL));

    for (int i = 0; i < k; i++)
    {
        temp = rand() % 25 + 97;

        for(int j=0; j<i; j++)
        {
            while(temp == sym[j])
            {
                temp = rand() % 25 + 97; // 25 means a and 122 means z
            }
        }

        sym[i] = temp;

    }

    for(int i=0; i<k; i++)
    {
        cout << sym[i] << endl;
    }
    return 0;
}

I still get duplicated results.

If temp == sym[1], you generate a new temp, but you do not recompare with sym[0]. — willll, Apr 10 '17 at 17:07
You can use `a` and `z` directly to calculate your constants. — François Andrieux, Apr 10 '17 at 17:11
`int sym[k];` is not standard C++ when `k` is not a constant expression and this should be avoided (prefer `std::vector`, if not possible, `new`). — crashmstr, Apr 10 '17 at 17:13

score 0 · Answer 1 · edited Jun 20 '20 at 09:12

0

Random generator doesn't mean unique generation, collisions can always happen especially when the number of generated values is high and the bounds or limits for the generation is small...

to avoid duplicated elements replace this array

int sym[k];

by a set which is a container that doesn't allow duplicate entries...

std::set<int>

after that, you need to replace the logic because looping k times does not mean having k elements in the set, so you need to do a while loop until the size of the set reaches the limit k

Edit:

if you need some unsorted generated values, the instead of using a set, consider implementing an unordered_set

edited Jun 20 '20 at 09:12

Community

1
1

answered Apr 10 '17 at 17:06

ΦXocę 웃 Пepeúpa ツ

47,427
17
69
97

A `set` is going to order the elements so that might not be desired. – NathanOliver Apr 10 '17 at 17:11
well he didnt specify about sort, in that case he need a unordered_set – ΦXocę 웃 Пepeúpa ツ Apr 10 '17 at 17:12
is there anyway to do this without using set or vector ? because I'm new to c++ and don't know about these things right now. – user3146643 Apr 10 '17 at 17:37
loop the array for insertion, generate a number but before inserting it in the array verify that value is not already there.... too much work.... – ΦXocę 웃 Пepeúpa ツ Apr 10 '17 at 17:42

score 0 · Answer 2 · answered Apr 10 '17 at 17:11

0

I will use std::unordered_set to avoid duplicated

answered Apr 10 '17 at 17:11

Patricio Rossi

167
2
5

Generating unique random characters and saving them in array

2 Answers2

Edit: