Create 2131.Longest-Palindrome-by-Concatenating-Two-Letter-Words.cpp

Author: wisdompeak

Hash/2131.Longest-Palindrome-by-Concatenating-Two-Letter-Words/2131.Longest-Palindrome-by-Concatenating-Two-Letter-Words.cpp

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+class Solution {
+public:
+    int longestPalindrome(vector<string>& words) 
+    {
+        unordered_map<string,int>count1;
+        unordered_map<string,int>count2;
+        unordered_map<string,int>count3;
+                
+        for (auto str: words)
+        {
+            string str2 = str;
+            reverse(str2.begin(), str2.end());
+            
+            if (str2==str)
+                count3[str]++;
+            else
+            {
+                string key = min(str2, str);
+                if (key==str)
+                    count1[key]++;
+                else
+                    count2[key]++;
+            }
+        }
+        
+        int ret = 0;
+        for (auto& [key, val]: count1)
+        {            
+            int a = count1[key];
+            int b = count2[key];
+            ret += min(a,b)*2*2;
+        }
+        int flag = 0;
+        for (auto& [key, val]: count3)
+        {
+            ret += val/2*2*2;
+            if (val%2==1)
+                flag = 1;
+        }
+        
+        return ret+flag*2;
+    }
+};