fd

Author: dingjikerbo

README.md

@@ -391,6 +391,7 @@
 |681|[Next Closest Time](https://leetcode.com/problems/next-closest-time/)|[Java](leetcode/solution/src/NextClosestTime.java)|80|这题多做几遍|
 |683|[K Empty Slots](https://leetcode.com/problems/k-empty-slots/)|[Java](leetcode/solution/src/KEmptySlots.java)|80||
 |684|[Redundant Connection](https://leetcode.com/problems/redundant-connection/)| [Java](leetcode/solution/src/RedundantConnection.java)|||
+|687|[Longest Univalue Path](https://leetcode.com/problems/longest-univalue-path/)|[Java](leetcode/solution/src/longestUnivaluePath.java)|70||
 |695|[Max Area of Island](https://leetcode.com/problems/max-area-of-island/)|[Java](leetcode/solution/src/MaxAreaOfIsland.java)|100||
 |703|[Kth Largest Element in a Stream](https://leetcode.com/problems/kth-largest-element-in-a-stream/)|[Java](leetcode/solution/src/KthLargestElementInAStream.java)|100||
 |771|[Jewels and Stones](https://leetcode.com/problems/jewels-and-stones/)|[Java](leetcode/solution/src/JewelsAndStones.java)|100||

leetcode/solution/src/CountUnivalueSubtrees.java

@@ -1,5 +1,8 @@
 public class CountUnivalueSubtrees {
 
+    /**
+     * 先分别判断左右子树是不是unival，如果是再判断带上root后是不是unival
+     */
     public int countUnivalSubtrees(TreeNode root) {
         int[] count = new int[1];
         helper(root, count);

leetcode/src/Main.java

@@ -6,8 +6,29 @@ public class Main {
 
     public static class Solution {
 
-        public List<TreeNode> generateTrees(int n) {
+        public int longestUnivaluePath(TreeNode root) {
+            int[] res = new int[1];
+            dfs(root, res);
+            return res[0];
+        }
+
+        private int dfs(TreeNode node, int[] res) {
+            if (node == null) {
+                return 0;
+            }
+            int left = dfs(node.left, res);
+            int right = dfs(node.right, res);
+
+            int lval = 0, rval = 0;
 
+            if (node.left != null && node.left.val == node.val) {
+                lval = left + 1;
+            }
+            if (node.right != null && node.right.val == node.val) {
+                rval = right + 1;
+            }
+            res[0] = Math.max(res[0], lval + rval);
+            return Math.max(lval, rval);
         }
     }