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src/main/java/com/dota/str/_2131/Solution.java

@@ -0,0 +1,36 @@
+package com.dota.str._2131;
+
+import java.util.HashMap;
+import java.util.Map;
+
+class Solution {
+	public static void main(String[] args) {
+		new Solution().longestPalindrome(new String[]{"em","pe","mp","ee","pp","me","ep","em","em","me"});
+	}
+	public int longestPalindrome(String[] words) {
+		Map<String, Integer> map = new HashMap<>();
+		for (String word : words) {
+			map.put(word, map.getOrDefault(word, 0) + 1);
+		}
+		var res = 0;
+		for (String word : words) {
+			if (map.get(word) == 0) {continue;}
+			if (word.charAt(0)==word.charAt(1) && map.get(word)==1) continue;
+			var s = ("" + word.charAt(1)) + word.charAt(0);
+			if (map.getOrDefault(s, 0) > 0) {
+				res += 4;
+				map.put(s, map.get(s) - 1);
+				map.put(word, map.get(word) - 1);
+			}
+		}
+		for (Map.Entry<String, Integer> entry : map.entrySet()) {
+			if (entry.getValue() > 0) {
+				var s = entry.getKey();
+				if (s.charAt(0) == s.charAt(1)) {
+					return res + 2;
+				}
+			}
+		}
+		return res;
+	}
+}