Create 2131. Longest Palindrome by Concatenating Two Letter Words

2131. Longest Palindrome by Concatenating Two Letter Words

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+class Solution {
+public:
+    int longestPalindrome(vector<string>& words) 
+    {
+        unordered_map<string, int> count;
+        unordered_set<string> visited, store;
+        for(auto &s : words) 
+        {
+            count[s] += 1;
+            store.insert(s);
+        }
+
+        int ans = 0, flag = true;
+        for(auto &s : store)
+        {
+            int cnt = count[s];
+            if(visited.count(s)) continue;
+            if(s[0] == s[1]) 
+            {
+                if(cnt % 2)
+                {
+                    cnt -= 1;
+                    if(flag)
+                    {
+                        ans += 2;
+                        flag = false;
+                    }
+                }
+                ans += cnt * 2;
+                continue;
+            }
+
+            string ss = string{ s[1], s[0] };
+
+            int cnt2 = count[ss];
+            int maxAdd = min(cnt, cnt2);
+            ans += (maxAdd * 2) * 2;
+
+            visited.insert(s);
+            visited.insert(ss);
+        }
+        return ans;
+    }
+};