count univalue subtrees

Author: fishercoder1534

MEDIUM/src/medium/CountUnivalueSubtrees.java

@@ -0,0 +1,32 @@
+package medium;
+
+import classes.TreeNode;
+
+public class CountUnivalueSubtrees {
+
+    public int countUnivalSubtrees(TreeNode root) {
+        int[] count = new int[1];
+        helper(root, count);
+        return count[0];
+    }
+
+    private boolean helper(TreeNode node, int[] count) {
+        if (node == null) {
+            return true;
+        }
+        boolean left = helper(node.left, count);
+        boolean right = helper(node.right, count);
+        if (left && right) {
+            if (node.left != null && node.val != node.left.val) {
+                return false;
+            }
+            if (node.right != null && node.val != node.right.val) {
+                return false;
+            }
+            count[0]++;
+            return true;
+        }
+        return false;
+    }
+
+}

README.md

@@ -63,6 +63,7 @@
 |259|[3Sum Smaller](https://leetcode.com/problems/3sum-smaller/)|[Solution](../../blob/master/MEDIUM/src/medium/_3Sum_Smaller.java)| O(n^2)|O(1) | Medium|
 |257|[Binary Tree Paths](https://leetcode.com/problems/binary-tree-paths/)|[Solution](../../blob/master/EASY/src/easy/BinaryTreePaths.java) | O(n*h) | O(h) | DFS/Recursion
 |252|[Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)|[Solution](../../blob/master/EASY/src/easy/MeetingRooms.java) | O(nlogn) | O(1) | 
+|250|[Count Univalue Subtrees](https://leetcode.com/problems/count-univalue-subtrees/)|[Solution](../../blob/master/MEDIUM/src/medium/CountUnivalueSubtrees.java)| O(n)|O(h) | Medium| DFS
 |249|[Group Shifted Strings](https://leetcode.com/problems/group-shifted-strings/)|[Solution](../../blob/master/EASY/src/easy/GroupShiftedStrings.java) | O(nlogn) | O(n) | 
 |246|[Strobogrammatic Number](https://leetcode.com/problems/strobogrammatic-number/)|[Solution](../../blob/master/EASY/src/easy/StrobogrammaticNumber.java) | O(n) | O(1) | 
 |243|[Shortest Word Distance](https://leetcode.com/problems/shortest-word-distance/)|[Solution](../../blob/master/EASY/src/easy/ShortestWordDistance.java) | O(n) | O(1) |