Create Maximum - Full Solution

Here is the complete approach:

function maxNumber(nums1, nums2, k)
 best := []
 for i from max(0, k - len(nums2)) to min(k, len(nums1))
 j := k - i
 candidate := merge(maxFromOne(nums1, i), maxFromOne(nums2, j))
 if candidate > best then
 best := candidate
 return best

Time: $O(k \cdot (n + m))$ for trying all splits and merging. Space: $O(k)$.

The range of $i$ ensures both arrays have enough digits for the split.