创建对称的二维数组

Question

I've been racking my brains over something that must be incredibly simple, as I've not seen it answered anywhere (or I'm very bad at searching).

I want to create a symmetrical 2D array, filled with random numbers from 1 to 100 inclusive... here is what I've got so far

int n = 3; int rangeOfWeights = 100;

    double[][] array = new double[n][n];
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < n; j++) {
            array[i][j] = rand.nextInt((rangeOfWeights)+1);         
        }
    }

At the moment, this is giving results like:

44 45 32 
9 31 53 
25 48 74 

when actually the kind of result I want is:

0 34 32
34 0 23
32 23 0

Answer 1

As you defined, you're trying to create a 2D array where array[i][j] == array[j][i] . You could a pair of nested loops where one iterates up to the array's size and the other up to the outer array's counter, and in each iteration set the value of the two symmetrical values:

double[][] array = new double[n][n];
for(int i = 0; i < n; i++) {
    for(int j = 0; j < i; j++) {
        int value = rand.nextInt((rangeOfWeights)+1);         
        array[i][j] = value;
        array[j][i] = value;
    }
}