Find Maximum Number of String Pairs
There are 676 possible 2-character strings.
So, we can use a boolean array to track if we’ve seen a string before.
Let’s break down the explanation in simpler terms and discuss how we can utilize a boolean array to solve this problem.
Understanding 2-Character Strings: Since the strings contain only 2 characters and are composed of lowercase English letters, there are a total of 26 * 26 = 676 possible 2-character strings. Think of it like a 26x26 grid, where each cell represents a unique combination of two letters.
Creating a Boolean Array: We can use a boolean array of size 676 to track if we have seen a particular 2-character string before. Each element in the array will correspond to one unique 2-character string. Initially, all elements will be set to
False
, meaning we haven’t seen any strings yet.Mapping Strings to Array Index: We need a way to map each 2-character string to a unique index in the boolean array. We can do this by converting the characters into their corresponding ASCII values and calculating the index as
index = (first_character - 'a') * 26 + (second_character - 'a')
.Tracking Reversed Strings: As we go through the given list of words, for each word, we’ll check if the reversed version of that word has been seen before by checking the corresponding index in the boolean array. If it has been seen, we can form a pair.
Updating the Array: After checking, we’ll update the boolean array for the current word, marking that we’ve seen this word.
Counting Pairs: We’ll keep track of the number of pairs we’ve found and return that as the result.
Code
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Key Takeaways
- By using a boolean array, we are efficiently tracking the existence of 2-character strings.
- This method helps us quickly identify pairs where one string is the reverse of the other.
- The solution is simple and direct, utilizing the fact that there are only 676 possible 2-character strings.