Java 2D数组-输入值

Question

Im implementing 2 algorithms for the TSP which uses a class which includes the routes, their cost, etc. At the minute it uses random values which is fine, although I now need to compare the algorithms so to make this fair I need to make the inputs the same (which is obviously unlikely to happen when using random inputs!) The issue im having is I dont know how to change it from random values to inserting pre-determined values into the 2D array, not just that but I also dont know how to calculate the costs of these values.

---

Randomly generates node values:

Random rand = new Random();
            for (int i=0; i<nodes; i++) {
                for (int j=i; j<nodes; j++) {
                    if (i == j)
                        Matrix[i][j] = 0;
                    else {
                        Matrix[i][j] = rand.nextInt(max_distance);
                        Matrix[j][i] = Matrix[i][j];
                    }
                }
            }

Im assuming for the above a declare a matrix of say [4][4] and then int matrix [][] = insert values ?

I do not help with some other sections of this class but I think I need to make sure this part is right before asking anymore!

Thanks a lot in advance!

Answer 1

You could set a seed instead for each random number generator therefore guaranteeing that for each implementation you test, the same sequence of pseudo-random numbers is being created.

This would save the effort of manually entering lots of values.

Edit to show seed method:

Random r = new Random(56);

Every time r is created with the seed of 56 it will produce the exact same sequence of random numbers. Without a seed I believe the seed is defaulted to the system time (giving the illusion of truly random numbers).

Answer 2

you can do initialization of 2D array like this:

    double matrix[][] = { { v1, v2, ..., vn }, { x1, x2, ..., xn }, ..., { y1, y2, ..., yn } };

where each inner {} represents the outter (first) index and each inner element represents the innermost (second) intex.

Example: to acess element x1 you do this:

    matrix[1][0];

This is the answer that you asked for, but I still think that it's better to use the same set of random values for both algorithms, Jon Taylor showed a good way for doing that. The code to set the seed looks like this:

    int seed = INTEGER_VALUE;
    Random rand = new Random(seed);

this way you will ever get the same set of values.