|18|[4 Sum](https://leetcode.com/problems/4sum/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_18.java)|O(n^2)|O(1)||Medium|Two Pointers

|17|[Letter Combinations of a Phone Number](https://leetcode.com/problems/letter-combinations-of-a-phone-number/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_17.java)|O(n*4^n)|O(n)||Medium|Backtracking

|16|[3Sum Closest](https://leetcode.com/problems/3sum-closest/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_16.java)|O(nlogn)|O(1)||Medium|Two Pointers

|14|[Longest Common Prefix](https://leetcode.com/problems/longest-common-prefix/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_14.java)| O(S) (S is the sum of all characters in all strings) | O(1)| [:tv:](https://www.youtube.com/watch?v=K1ps6d7YCy4)| Easy

|13|[Roman to Integer](https://leetcode.com/problems/roman-to-integer)|[Solution](../master/src/main/java/com/fishercoder/solutions/_13.java)| O(1) | O(1) | |Easy | Math, String

|12|[Integer to Roman](https://leetcode.com/problems/integer-to-roman/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_12.java)|O(1)|O(1)||Medium| Math, String