DiameterOfBinaryTree543

Author: fluency03

Diff for: README.md

@@ -32,11 +32,11 @@
 
 
 
-# Total: 166
+# Total: 167
 
 | Easy | Medium | Hard |
 |:----:|:------:|:----:|
-|  36  |   98   |  32  |
+|  37  |   98   |  32  |
 
 
 | Question | Solution | Difficulty |
@@ -192,6 +192,7 @@
 | [513. Find Bottom Left Tree Value](https://leetcode.com/problems/find-bottom-left-tree-value/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/FindBottomLeftTreeValue513.java) | Medium |
 | [525. Contiguous Array](https://leetcode.com/problems/contiguous-array/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/ContiguousArray525.java) | Medium |
 | [535. Encode and Decode TinyURL](https://leetcode.com/problems/encode-and-decode-tinyurl/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/EncodeAndDecodeTinyURL535.java) | Medium |
+| [543. Diameter of Binary Tree](https://leetcode.com/problems/diameter-of-binary-tree/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/DiameterOfBinaryTree543.java) | Easy |
 | [547. Friend Circles](https://leetcode.com/problems/friend-circles/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/FriendCircles547.java) | Medium |
 | [554. Brick Wall](https://leetcode.com/problems/brick-wall/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/BrickWall554.java) | Medium |
 | [560. Subarray Sum Equals K](https://leetcode.com/problems/subarray-sum-equals-k/) | [Solution](https://github.com/fluency03/leetcode-java/blob/master/src/SubarraySumEqualsK560.java) | Medium |

Diff for: src/DiameterOfBinaryTree543.java

@@ -0,0 +1,44 @@
+/**
+ * Given a binary tree, you need to compute the length of the diameter of the
+ * tree. The diameter of a binary tree is the length of the longest pathbetween
+ * any two nodes in a tree. This path may or may not pass through the root.
+ *
+ * Example:
+ * Given a binary tree
+ *           1
+ *          / \
+ *         2   3
+ *        / \
+ *       4   5
+ * Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].
+ *
+ * Note: The length of path between two nodes is represented by the number of
+ * edges between them.
+ *
+ */
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+
+public class DiameterOfBinaryTree543 {
+    public int diameterOfBinaryTree(TreeNode root) {
+        return helper(root)[0];
+    }
+
+    private int[] helper(TreeNode root) {
+        if (root == null) return new int[]{0, 0};
+
+        int[] l = helper(root.left);
+        int[] r = helper(root.right);
+
+        return new int[]{Math.max(Math.max(l[0], r[0]), l[1] + r[1]), Math.max(l[1], r[1]) + 1};
+    }
+
+}