generate 20 distinguish random numbers

[tina123]

I want to generate random numbers from 1 to 20.
how can i do it?

I did something like this .

#include <stdio.h>
#include <stdlib.h>
/* function main begins program execution */

int main(void) 
{
    int i, j ;                           /* counter */
	/* loop 20 times */
	for (i = 1; i <= 20; i++) 
    {
       /* pick random number from 1 to 6, but random numbesr 
       shoudl not be duplicte. and output it */
		printf("%d ", 1 + (rand() % 20));
            
    
	} /* end for */
	return 0; /* indicates successful termination */
} /* end main */

but i don't need duplicate random numbers.
how can i get it?
Pls help me. thanks

[abhishekm71]

Insert the elements 1 to 20 in a list.
set initial i = 20.
generate random number between 1 and i.
output the ith list number and delete that number from the list.
decrement count and repeat till you have all the twenty numbers.

[MrHutch]

You could have a vector of numbers that have already been generated and check any newly generated numbers against that.

Or, since you seem to be using C, an array.

[AbstractionAnon]

Create an array of 20 ints along with a count of how many random numbers are in the array.

When you generate a random number, check if it's already in the array. If it is, skip it and generate another random number.

You will need to change your for loop to a while loop since you won't know in advance how many times you will need to call rand() to get a unique random number.

[tina123]

Hye @abstractionAnon, Can u pls explain your answer with modification in my program. thanks

[abhishekm71]

use can use shuffle algorithm to randomly rearrange the numbers 1 to 20 preinserted in an array.