Write a method named isUnique that accepts a 2-D array of integers as a parameter and that returns a boolean value indicating whether or not the values in the array are unique (true for yes, false for no). The values in the list are considered unique if there is no pair of values that are equal.

For example, if a variable called matrix stores the following values:

int[][] matrix = {{3, 8, 12}, {2, 9, 17}, {43, -8, 46}, {203, 14, 97}};

Then the call of isUnique(matrix) should return true because there are no duplicated values in this array. If instead the array stored these values:

int[][] matrix2 = {{4, 7, 2}, {3, 9, 12}, {-47, -19, 308}, {3, 74, 15}};

Then the call should return false because the value 3 appears twice in this list. Notice that given this definition, an array of 0 or 1 elements would be considered unique. Your code should work for an array of any size, even one with 0 rows or columns.

Constraints: You may use one auxiliary data structure of your choice to help you solve this problem. Your method should not modify the array that is passed in.