Problem Description
Given a multi-dimensional array of integers (which may contain further nested arrays), implement a generator that yields integers in the same order as an inorder traversal (i.e. process the current list from left to right, recursively traversing any nested arrays). The solution must not create a fully flattened copy of the array.
Key Insights
- Use recursive traversal to process arbitrarily nested arrays.
- Yield integers immediately when encountered; do not accumulate them in an auxiliary container.
- Leverage language features such as generator functions (Python, JavaScript) or implement lazy iterators using a stack or coroutines (Java, C++).
- This approach minimizes extra space usage by avoiding full flattening.
Space and Time Complexity
Time Complexity: O(n), where n is the total number of elements (including nested arrays) since each element is visited exactly once. Space Complexity: O(d), where d is the maximum nesting depth (used by the recursion or stack).
Solution
The solution uses a recursive approach to traverse the nested structure. In languages with native generator support, a recursive generator function is defined to yield each integer as soon as it’s processed. In languages without native generators, we simulate this behavior by implementing an iterator using a stack (or, in C++20, using coroutines). This lazy evaluation avoids creating a new, flattened list and keeps extra space usage to the current recursion/stack depth.