Modify the binary search algorithm so that it returns an array of length 2 with the lowest index and highest index of those element(s) that equal the searched value.

For example, when searching for 3, if the array contains the values 1 1 3 3 3 4 5 5, the algorithm should return [2, 4].

If the value is not found, return an array of length 1 containing the index at which the value should be inserted.

Your implementation should have O(log n) running time even if most elements of the array have the same value.