2744. Find Maximum Number of String Pairs

You are given a 0-indexed array words consisting of distinct strings.

The string words[i] can be paired with the string words[j] if:

• The string words[i] is equal to the reversed string of words[j].
• 0 <= i < j < words.length.

Return the maximum number of pairs that can be formed from the array words.

Note that each string can belong in at most one pair.

class Solution {
public:
    int maximumNumberOfStringPairs(vector<string>& words) {
        unordered_set<string> us;
        int res = 0;
        for(auto w : words) {
            if(us.count(w)) res += 1;
            reverse(begin(w), end(w));
            us.insert(w);
        }
        return res;
    }
};