I am creating a 5x5 board game in C. The problem I am having is that when I use the rand() it duplicates some of the numbers. How do I stop the duplicates and 0's?
Sorry if too basic a question. I'm new to C.
int createboard() {
int rows;
int columns;
int board[5][5];
int board2[5][5];
srand(time(NULL));
for (rows = 0; rows < 5; rows++) {
for (columns = 0; columns < 5; columns++) {
randomNumber = rand() % 25;
board[rows][columns] = randomNumber;
}
}
}
rand() would not be a particularly good generator if the probability of drawing the same number twice was zero.
A standard approach here would be to generate the board with consecutive numbers, then shuffle it by swapping elements at random a certain number of times.
A good shuffling algorithm is https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
Use srand() function instead of rand function. rand() will give same numbers after each program. Refer this for help. This is for improvement of your program this is not answer Rand() vs srand() function
Deleted since downvoted. That is a reason why it is removed.
rand implementation draws numbers in its periodic cycle such that when the results are transformed under the function % 25, they completely fill the range [0, 24]. The C standard makes no such guarantees (a trivial counterexample would be a rand implementation that draws only even numbers), so this approach could cause an infinite loop. Granted, this is unlikely but it does illustrate an important flaw in this technique.
rand is intended to select from the integers in [0, RAND_MAX] with uniform distribution. A rand that returned only even values (always, not just in some limited subsequence) would be defective.
rand(). You clearly don't want random numbers; you want a random order of a specific set of numbers, which is a very different thing, so generating random numbers isn't the answer.