What's the relationship between time complexity and complement?
I do not understand what complement means to be used.
I do not understand the sentence below.
Approach #2 (Two-pass Hash Table) [Accepted]
To improve our run time complexity, we need a more efficient way to check if the complement exists in the array. If the complement exists, we need to look up its index. What is the best way to maintain a mapping of each element in the array to its index? A hash table.
Complement refers to the other number that when added to the current number will give you the value of the target.
If (for all) a + b = target, then a's complement is b.
In order to see if a complement of a number is there, instead of looping through the array (which is O(n)), they are storing it (the elements in the source array) is a hash map.