|544|[Output Contest Matches](https://leetcode.com/problems/output-contest-matches/)|[Solution](../master/src/main/java/com/fishercoder/solutions/OutputContestMatches.java) | O(n) |O(n) | Medium | Recursion

|543|[Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_543.java) | O(n) |O(h) | Easy | Tree/DFS/Recursion

|542|[01 Matrix](https://leetcode.com/problems/01-matrix/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_542.java) | O(m*n) |O(n) | Medium | BFS

|540|[Single Element in a Sorted Array](https://leetcode.com/problems/single-element-in-a-sorted-array/)|[Solution](../master/src/main/java/com/fishercoder/solutions/SingleElementinaSortedArray.java) | O(n) |O(1) | Medium |

|539|[Minimum Time Difference](https://leetcode.com/problems/minimum-time-difference/)|[Solution](../master/src/main/java/com/fishercoder/solutions/MinimumTimeDifference.java) | O(n) |O(1) | Medium | String

|538|[Convert BST to Greater Tree](https://leetcode.com/problems/convert-bst-to-greater-tree/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_538.java) | O(nlogn) |O(n) | Medium | Tree

public String reverseStr(String s, int k) {

StringBuilder stringBuilder = new StringBuilder();

package com.fishercoder;

import org.junit.Before;

import org.junit.BeforeClass;

import org.junit.Test;

import static junit.framework.Assert.assertEquals;

private static String expected;

private static String actual;

private static String s;

private static int k;

@BeforeClass

public static void setup(){

}

@Before