Picking random chars from char array?

[oenigmaa]

Hello!

I'm very new to C++ and have a pretty daunting assignment due this week. I won't get into too much detail about it as I don't want work done for me, but can anyone point me in the right direction as to how I would go about picking random characters from a multi-dimensional string array?

char gameZero[16][6] = { {'A','A','C','I','O','T'}, {'A','H','M','O','R','S'}, {'E','G','K','L','U','Y'}, {'A','B','I','L','T','Y'}, {'A','C','D','E','M','P'}, {'E','G','I','N','T','V'}, {'G','I','L','R','U','W'}, {'E','L','P','S','T','U'}, {'D','E','N','O','S','W'}, {'A','C','E','L','R','S'}, {'A','B','J','M','O','Q'}, {'E','E','F','H','I','Y'}, {'E','H','I','N','P','S'}, {'D','K','N','O','T','U'}, {'A','D','E','N','V','Z'}, {'B','I','F','O','R','X'} };

The goal is to print out a 4x4 board of these characters, picking one random character from each array at the start of every game so not one board is the same.

Any advice/tips on how to do this would be greatly appreciated-- thank you!

[Duthomhas]

Use a RNG with a std::uniform_int_distribution to select. Now you just need a loop for each sub-array of the gameZero array.

Use the Search box at the top of the site to find documentation on these objects, including some nice examples.

Good luck!

[Ganado]

Generate a random number from 0-15 for the outer array.
Generate a random number from 0-5 for the inner array.
Select the character at that array index.

#include <iostream>
#include <random>
#include <ctime>

int main()
{
	constexpr int outer_size = 16;
	constexpr int inner_size = 6;
	char game[outer_size][inner_size] = { /* ... */ };
	
	// filling with 'A' just for example
	for (int i = 0; i < outer_size; i++)
	for (int j = 0; j < inner_size; j++)
		game[i][j] = 'A';

	std::mt19937 gen(time(nullptr)); // random number generator, seeded based on current time

	// Used to generate a random number in specific range [a, b]:
	std::uniform_int_distribution<int> random_outer(0, outer_size - 1); // inclusive range!
	std::uniform_int_distribution<int> random_inner(0, inner_size - 1);

	int index_outer = random_outer(gen); // generate the random outer index
	int index_inner = random_inner(gen); // generate the random inner index
	
	// print the value
	std::cout << game[index_outer][index_inner] << '\n';
}

[Duthomhas]

Er, yes, outer dimension too...

Sorry I missed that.

[oenigmaa]

I'm not too sure how to reply or directly quote yet, but I very much appreciate the speedy responses. I'm going to work on this now-- thank you both!

[oenigmaa]

@garnado

This worked and now picks a random character from the arrays-- thank you!

I'm assuming some funky for loop has to come into play, but I'm having trouble working out a solution to now print one of these characters from EACH of the 16 arrays. I essentially need to take one random character from all 16 and implement them into a word game.

Would I have to put the generators (random_outer & random_inner) in a loop to generate 16 different indices?

[oenigmaa]

I had a bit of an idea (again, pretty new to coding in general so this may make almost no sense at all)--

To get an outcome in the reply above, should I loop through the outer 16 elements and only generate random numbers for the inner elements?

This way, I can make i<outer_size, and cout something like:

cout<<gameZero[i][/*whatever random number is chosen*/]<<endl;

[Ganado]

If you wanted to print the Nth inner character from each outer array, you'd do something like

int n = random_inner(gen); // generate the random inner index
for (int i = 0; i < 16; i++)
{
	cout << gameZero[i][n] << '\n';
}

[doug4]

It looks to me like you trying to simulate the game Boggle.

The suggestions above show you how to get random numbers. For a beginner, I'm not sure they provide any benefit over srand() and rand().

If this is the Boggle game, the issue you have is that each die must be used 1 time. So, you need to do the following:

Randomize the order of the die indices (0 - 15). So you will have an array like :
i[0]= 12
i[1] = 0
i[2] = 7
etc.

Each array element is the outer index into the gameZero array.

Now you want to map the i array onto your game board. Each element of i now points to a die from gameZero. Randomize the side of the die, and place the resultant letter into your game board.

Something like this (not tested):

for (row = 0; row < 4; ++row)
{
   for (col = 0; col < 4; ++col)
   {
      int side = rand() % 6;
      int dieIndex = i[(row * 4) + col];
      game[row][col] = gameZero[dieIndex][side];
   }
}