CreateMatrix makes an array of array by rows * columns.

GetProducts returns a new array where the value at any index has the products of all the other numbers in a given integer array.

InsertIntoSlice inserts the value into the slice at the specified index, which must be in range and the slice must have room for the new element.

Maps func.

Reduce func.

Reverse func re-arranges array items reversely.

Shift func to get the first item in slice and shifted the rest.