refactor 18

Author: Steve Sun

.gitignore

@@ -4,4 +4,5 @@ gradlew
 gradlew.bat
 .DS_Store
 build/
+out/
 

src/main/java/com/fishercoder/solutions/_18.java

@@ -4,7 +4,11 @@
 import java.util.Arrays;
 import java.util.List;
 
-/**Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target.
+/**
+ * 18. 4Sum
+ *
+ * Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target?
+ * Find all unique quadruplets in the array which gives the sum of target.
 
  Note: The solution set must not contain duplicate quadruplets.