Create 409. Longest Palindrome (#494)

Author: Chayandas07

409. Longest Palindrome

@@ -0,0 +1,17 @@
+class Solution {
+public:
+    int longestPalindrome(string s) {
+        int c = 0; // odd count
+        unordered_map<char, int>m;
+        for(auto ch : s) {
+            m[ch]++;
+            if (m[ch] & 1)
+                c++;
+            else    
+                c--;
+        }
+        if (c > 1)
+            return s.length() - c + 1;
+        return s.length();
+    }
+};