Discussions

Intuition + complexity breakdown for Roman to Integer. Use a hash map from value to index (or count). For each element check whether its complement is already in the map, then insert it. That makes it O(n) instead of the O(n²) brute force.

Asked in my Paytm OA last week. Use a hash map from value to index (or count). For each element check whether its complement is already in the map, then insert it. That makes it O(n) instead of the O(n²) brute force.

Finally got AC after 3 WAs. Sharing what I missed. Use a hash map from value to index (or count). For each element check whether its complement is already in the map, then insert it. That makes it O(n) instead of the O(n²) brute force.