int[][] array = new int[5][5];
for (int i = 0; i < array.length; i++) {
for (int j = 0; j < array.length; j++) {
System.out.print(1);
}
System.out.println();
}
Hi guys, i have this array which prints a 5x5 1's
11111
11111
11111
11111
11111
What i would like to do is to make three (3) of those 1's as 0 randomly. Example
11101
11111
11011
10111
11111
How do I do that? Thank you in advance!
You would have to firstly initialize the array with 1s:
int[][] array = new int[5][5];
for (int i = 0; i < array.length; i++) {
for (int j = 0; j < array.length; j++) {
array[i][j] = 1;
}
}
Then set 0s in 3 random positions:
Random random = new Random();
int a = 0;
while (a < 3) {
int i = random.nextInt(array.length);
int j = random.nextInt(array[0].length);
if(array[i][j] != 0) {
array[i][j] = 0;
a++;
}
}
Using this approach each entry in the array has the same chance of becoming a 0. Finally you should print the array:
for (int i = 0; i < array.length; i++) {
for (int j = 0; j < array.length; j++) {
System.out.print(array[i][j]);
}
System.out.println();
}
For random stuff, you can use Math.random(). It returns a random double between 0 included and 1 excluded. You could do this :
int w = 5, h = 5;
int[][] array = new int[w][h];
for (int i = 0; i < w; i++) {
for (int j = 0; j < h; j++) {
array[i][j] = 1;
}
}
for (int c = 0; c < 3; c++) {
int i, j;
do {
int index = (int)(Math.random() * w * h);
i = index / w;
j = index % w;
} while (array[i][j] == 0);
array[i][j] = 0;
}
This solution is acceptable only if the number of 0 is low compared to the total size of the array. If the number of 0 is too high this code is going to be very inefficient because we will search randomly for a value of 1
Here is a slightly different solution for fun. Create an list with numbers from 0 to 24, shuffle the list and pick the the 3 first elements from it to update the 2D array. The sequence of numbers means that not the same position in the array will be set to 0 more than once.
List<Integer> sequence = IntStream.rangeClosed(0, 24)
.boxed()
.collect(Collectors.toList());
Collections.shuffle(sequence);
for (int i = 0; i < 3; i++) {
int value = sequence.get(i);
int row = value / 5;
int column = value % 5;
array[row][column] = 0;
}
The code for generating the sequence came from this answer
