Write a method findDouble that takes in 2 arguments: the first argument is a 2D array of Doubles called
values (Array<DoubleArray>?), and the second argument is a Double called target. Your method will return
the target number if it exists in a non-diagonal element of values, or return -1.0 otherwise (if
values does NOT contain target in a non-diagonal element). You may assume the values array will always
be square (same number of rows as columns). If values is null or empty, return -1.0.
Examples: If values = [[1.0, 2.0], [3.0, 4.0]] and target = 2.0, then findDouble returns 2.0.
If values = [[3.0]] and target = 3.0,
then findDouble returns -1.0 because target is in a diagonal element (even though it is present in values).
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