i'm trying to make a console 2048 game in Java, i'd like to implement a rotation of the board by 90 degrees to the right, i searched on the web and implemented a function but it's not swapping every rows and colums, could someone please review what i wrote and help me pinpoint the actual error in my code.
public static void rotation90Droite(int [][] vals) {
int e = vals.length-1;
int c = e / 2;
for (int i = 0; i <= c ; i++) {
for (int j = i; j <e - i; j++) {
int t = vals[i][j];
vals[i][j] = vals[e - j][i];
vals[e - j][i] = vals[e - i][e - j];
vals[e - i][e - j] = vals[j][e - i];
vals[j][e - j] = t;
}
}
}
public static void printMatrix(int[][] Matrix) {
for(int i = 0; i < Matrix.length; i++) {
for (int j = 0; j < Matrix.length; j++) {
System.out.print(Matrix[i][j]+ " ");
}
System.out.println(" ");
}
}
public static void main(String[] args) {
int[][] vals = {{1,2,3,4},{5,6,7,8},{9,10,11,12},{13,14,15,16}} ;
printMatrix(vals);
System.out.println(" ");
rotation90Droite(vals);
printMatrix(vals);
}
}
This should actually make the first row become the last column, the last column become the last row etc...
what i'm actually getting is :
1 2 3 4
5 6 7 8 // Starting matrix
9 10 11 12
13 14 15 16
13 9 5 1
14 3 6 8 // end matrix
15 11 2 12
16 12 8 4
As you can see the last row swaped correctly but so muchs values are not in the right place, i can't find why. Any help will be appreciated thanks you by advance
Geometric problems like this usually have a pattern to how you're accessing the elements of your array. If you read through the indices you're using, the last assignment in your loop doesn't quite match the pattern:
vals[j][e - j] = t;
should be:
vals[j][e - i] = t;
Here's a working demo.
For the future, learning to use a debugger will be an extremely valuable tool for solving these sorts of problems.