How to print characters in array in random order???

Question

Hello, so I'm kind of stuck. I am writing a C code which allows a user to enter their student number, then choose whether they want their student number written in the forwards direction, backwards or in random order.
I am unsure how to randomize the characters entered into the array so I can then print them out in random order. Wonder if anyone can help?

Here is how far I got:
#include <stdio.h>
#include <stdlib.h>
#include<string.h>

int main(void)
{
char fbr;
int i;
char name[9]; // char string as an array of characters

printf("Please enter student number: ");
//prompt user to enter student number

scanf("%s", name);
//accept input from user

getchar();
// required to avoid return key being recognised as a character

printf("\nYour student number has been entered. Please type f to print in forward direction, b to print backwards or r for random: \n\n");

scanf("%c", &fbr);

if (fbr == 'f')

//Print student number in the Forward Direction
for(i=0; i<9; i++)
{
printf("%c",name[i]);
}

else if (fbr == 'b')

// Print student number in the Reverse Direction
for(i=8; i>=0; i--)
{
printf("%c",name[i]);
}

else if (fbr == 'r')
{
// Print student number Randomly

}

else
{
printf("\n\n hmmmmm \U0001F914 looks like you have entered an invalid option, please restart program and try again;");
}
return 0;
}

\\end of code

Thanks

Answer 1

Use rand() can generate a random number.

srand(time(NULL)); //seed based on time. #include <time.h>
printf("%d", rand()%9);

And then you can access a random index of characters. But you will need a way to avoid duplicate index access.

Answer 2

So I think this post could be the answer,

https://www.sololearn.com/discuss/1696414/?ref=app
https://www.sololearn.com/discuss/1460769/?ref=app
https://www.sololearn.com/discuss/279538/?ref=app
https://www.sololearn.com/discuss/2062227/?ref=app

Answer 3

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

void swap(int *a, int *b)
//swap function use to help randomise array
{
int temp = *a;
*a = *b;
*b = temp;
}

void randomise(int arr[], int n)
//randomise function to shuffle the array for random option in program
{
srand(time(NULL)); //seed based on time
int i;
for(i = n-1; i > 0; i--) {
int j = rand() % (i+1);
//rand() used to generate a random number
swap(&arr[i], &arr[j]);
}
}

int main(void)
{
int arr[] = {0, 1, 2, 3, 4, 5, 6, 7, 8 };
//array of integers to index the 8 char of student number
int n = sizeof(arr)/ sizeof(arr[0]);
char fbr;
int i;
char name[9];
// char string as an array of characters

printf("Please enter student number: ");
//prompt user to enter student number

scanf("%s", name);
//accept input from user

getchar();
// required to avoid return key being recognised as a character

printf("\nYour student number has been entered. Please type f to print in forward direction, b to print backwards or r for random: \n\n");

scanf("%c", &fbr);

if (fbr == 'f')

//Print student number in the Forward Direction
for(i=0; i<9; i++)
{
printf("%c",name[i]);
}

else if (fbr == 'b')

// Print student number in the Reverse Direction
for(i=8; i>=0; i--)
{
printf("%c",name[i]);
}

else if (fbr == 'r')
{
// Print student number Randomly
randomise (arr, n);
for(i=0; i<n; i++)
// print the array products using the randomised indexes
{
int index = arr[i];
printf("%c",name[index]);
}
}

else
// give error if neither 'f', 'b' or 'r' are chosen as options
{
printf("\n\n hmmmmm \U0001F914 looks like you have entered an invalid option, please restart program and try again;

Answer 4

Thanks guys, got it figured out 👍

Answer 5

Thanks for those points Martin.
So if I wanted the code to ignore spaces and keep reading until it collects all the required characters I would have to get rid of scanf altogether and use something along the lines of fgets() instead?

Link to code: https://code.sololearn.com/cyS8Kr8P9qne