Question

Need to put the frequency of each number occurrence into a 1D array and output the result. The 2D to 1D part is throwing me off, I’m not terribly comfortable with arrays yet.

public static void main( String[] args ){

  int matrix [][]=new int[20][2];

  for (int row=0;row<matrix.length;row++){
    for (int column=0;column<matrix[row].length;column++)
      matrix[row][column]=(int)(Math.random()*12+1);

  }
   frequency(matrix);




public static int frequency(int [][] matrix){
   int [] nums =[12];
   int count =0;
   for (int i=0;i<matrix.length;i++){
      for (int j=0; j<matrix[i].length;j++)
            (???)

       }
   return (?);

Answer 1

Something like this I would guess :

public static int[] frequency(int [][] matrix){
    int [] nums =[14];      // max value can be 13 so you need 14 element
    int count =0;
    for (int i=0;i<matrix.length;i++){
        for (int j=0; j<matrix[i].length;j++) {
            nums[matrix[i][j]] += 1;
        }
    }
    return nums;
}

This is a bit of a contrived example, as normally the values to be collected do not nicely fall on an array index, so a hashmap would be a more typical solution.

Actually it would be more fun to multiply 2 random numbers (Like Math.random()*Math.random() + 1 ) to fill the matrix, then you get a nice bell curve instead of boring white noise in your final frequency distribution.