Test Case 1 In the brute-force approach to generating substrings using nested loops, maintaining a hashmap that counts each character's occurrence as 1 (e.g., setting counts to 1 regardless of actual frequency) is invalid. Proper substring generation and validation require accurately tracking character counts in the hashmap rather than assuming all characters occur only once. geekforgeeks eekforgeeks ekforgeeks kforgeeks forgeeks orgeeks rgeeks geeks eeks eks ks s Test Case 2 From the following output, what we actually need is a contiguous substring of characters that satisfies our problem constraints. For example, in the second case, the longest substring without repeating characters is 'ksforg' or 'stoare'—these substrings are contiguous and contain no repeating characters. geekforgeeks eekforgeek ekforgee kforge forg or o Test Case 3 We can use a fixed-size sliding window to find substrings. Starting with a window of fixed size, we keep decreasing the w...