Split Concatenated Strings - Video Solutions

Problem Overview: You receive an array of strings. Each string can either stay as is or be reversed before concatenation. After forming the final concatenated string, you can split it at any position and swap the order of the two parts. The goal is to return the lexicographically largest possible string after these operations.

Approach 1: Brute Force Enumeration (Exponential Time)

Try every possible orientation for each string: original or reversed. With n strings, that creates 2^n combinations. For each combination, concatenate the strings, then simulate every possible split point and compare the resulting rotated strings to keep the maximum lexicographic result. This approach clearly demonstrates the full search space but quickly becomes impractical. Time complexity is O(2^n * L^2) where L is the total concatenated length, and space complexity is O(L).

Approach 2: Greedy with Optimal Orientation (O(n * L^2))

The key greedy observation: for every string, keeping the lexicographically larger version between the original and its reverse will always help maximize the final result. First iterate through the array and replace each string with max(s, reverse(s)). This ensures every segment contributes the largest possible prefix when concatenated.

Next, treat each string as a potential split source. For the current index i, consider both orientations of that string (s and reverse(s)) because the split may occur inside it. Build the remaining concatenation using the already optimized orientation for other strings. Then iterate through every split position inside the chosen string and construct a candidate result: suffix + rest_of_strings + prefix. Track the maximum lexicographic string during this process.

This works because the greedy preprocessing fixes all strings except the one containing the split. Only that string might need reconsideration of orientation. If the total length of all strings is L, evaluating every split across all strings results in O(n * L^2) time in the worst case with O(L) auxiliary space.

The solution combines ideas from greedy decision making with careful iteration over string rotations and indexing within an array of words.

Recommended for interviews: The greedy approach is what interviewers expect. Mentioning the brute-force 2^n orientation search shows you understand the full problem space, but recognizing that each string should first be normalized to its lexicographically larger orientation demonstrates algorithmic insight and reduces the search dramatically.