refactor 409

Author: fishercoder1534

README.md

@@ -373,6 +373,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |412|[Fizz Buzz](https://leetcode.com/problems/fizz-buzz/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_412.java)| O(n)|O(1) | |Easy|
 |411|[Minimum Unique Word Abbreviation](https://leetcode.com/problems/minimum-unique-word-abbreviation/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_411.java)| O(?)|O(?) | |Hard| NP-Hard, Backtracking, Trie, Recursion
 |410|[Split Array Largest Sum](https://leetcode.com/problems/split-array-largest-sum/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_410.java)| O(nlogn)|O(1) | |Hard| Binary Search, DP
+|409|[Longest Palindrome](https://leetcode.com/problems/longest-palindrome/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_409.java)| O(n)|O(1) | |Easy| 
 |408|[Valid Word Abbreviation](https://leetcode.com/problems/valid-word-abbreviation/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_408.java)| O(n)|O(1) | |Easy|
 |407|[Trapping Rain Water II](https://leetcode.com/problems/trapping-rain-water-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_407.java)| | | |Hard| Heap
 |406|[Queue Reconstruction by Height](https://leetcode.com/problems/queue-reconstruction-by-height/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_406.java)| O(nlogn)|O(1) | |Medium| LinkedList, PriorityQueue

src/main/java/com/fishercoder/solutions/_409.java

@@ -0,0 +1,48 @@
+package com.fishercoder.solutions;
+
+/**
+ * 409. Longest Palindrome
+ *
+ * Given a string which consists of lowercase or uppercase letters, find the length of the longest palindromes that can be built with those letters.
+ * This is case sensitive, for example "Aa" is not considered a palindrome here.
+ *
+ * Note:
+ * Assume the length of given string will not exceed 1,010.
+ *
+ * Example:
+ * Input:
+ * "abccccdd"
+ *
+ * Output:
+ * 7
+ *
+ * Explanation:
+ * One longest palindrome that can be built is "dccaccd", whose length is 7.
+ */
+public class _409 {
+  public static class Solution1 {
+    public int longestPalindrome(String s) {
+      int[] counts = new int[56];
+      for (char c : s.toCharArray()) {
+        if (Character.isUpperCase(c)) {
+          counts[c - 'A' + 33]++;
+        } else {
+          counts[c - 'a']++;
+        }
+      }
+      boolean hasOdd = false;
+      int len = 0;
+      for (int i = 0; i < 56; i++) {
+        if (counts[i] % 2 != 0) {
+          hasOdd = true;
+          if (counts[i] > 1) {
+            len += counts[i] - 1;
+          }
+        } else {
+          len += counts[i];
+        }
+      }
+      return hasOdd ? len + 1 : len;
+    }
+  }
+}

src/test/java/com/fishercoder/_409Test.java

@@ -0,0 +1,37 @@
+package com.fishercoder;
+
+import com.fishercoder.solutions._409;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class _409Test {
+  private static _409.Solution1 solution1;
+
+  @BeforeClass
+  public static void setup() {
+    solution1 = new _409.Solution1();
+  }
+
+  @Test
+  public void test1() {
+    assertEquals(7, solution1.longestPalindrome("abccccdd"));
+  }
+
+  @Test
+  public void test2() {
+    assertEquals(7, solution1.longestPalindrome("abccAccdd"));
+  }
+
+  @Test
+  public void test3() {
+    assertEquals(983, solution1.longestPalindrome(
+        "civilwartestingwhetherthatnaptionoranynartionsoconceivedandsodedicatedcanlongendureWeareqmetonagreatbattlefiemldoftzhatwarWehavecometodedicpateaportionofthatfieldasafinalrestingplaceforthosewhoheregavetheirlivesthatthatnationmightliveItisaltogetherfangandproperthatweshoulddothisButinalargersensewecannotdedicatewecannotconsecratewecannothallowthisgroundThebravelmenlivinganddeadwhostruggledherehaveconsecrateditfaraboveourpoorponwertoaddordetractTgheworldadswfilllittlenotlenorlongrememberwhatwesayherebutitcanneverforgetwhattheydidhereItisforusthelivingrathertobededicatedheretotheulnfinishedworkwhichtheywhofoughtherehavethusfarsonoblyadvancedItisratherforustobeherededicatedtothegreattdafskremainingbeforeusthatfromthesehonoreddeadwetakeincreaseddevotiontothatcauseforwhichtheygavethelastpfullmeasureofdevotionthatweherehighlyresolvethatthesedeadshallnothavediedinvainthatthisnationunsderGodshallhaveanewbirthoffreedomandthatgovernmentofthepeoplebythepeopleforthepeopleshallnotperishfromtheearth"));
+  }
+
+  @Test
+  public void test4() {
+    assertEquals(3, solution1.longestPalindrome("ccc"));
+  }
+}