feat: 每日一题更新2019-07-04

Author: luzhipeng

Diff for: daily/2019-07-04.md

@@ -0,0 +1,96 @@
+## 每日一题 - longest-univalue-path
+
+### 信息卡片
+
+- 时间：2019-07-04
+- 题目链接：https://leetcode.com/problems/longest-univalue-path/
+- tag：`recursive` `tree`
+
+### 题目描述
+
+```
+Given a binary tree, find the length of the longest path where each node in the path has the same value. This path may or may not pass through the root.
+
+The length of path between two nodes is represented by the number of edges between them.
+
+ 
+
+Example 1:
+
+Input:
+
+              5
+             / \
+            4   5
+           / \   \
+          1   1   5
+Output: 2
+
+ 
+
+Example 2:
+
+Input:
+
+              1
+             / \
+            4   5
+           / \   \
+          4   4   5
+Output: 2
+
+ 
+
+Note: The given binary tree has not more than 10000 nodes. The height of the tree is not more than 1000.
+
+```
+
+### 参考答案
+
+```js
+/*
+ * @lc app=leetcode id=687 lang=javascript
+ *
+ * [687] Longest Univalue Path
+ */
+
+// 返回经过root的且只能取左右一个节点的路径长度
+function helper(node, res) {
+    if (node === null) return 0;
+    const l = helper(node.left, res);
+    const r = helper(node.right, res);
+    let lcnt = 0;
+    let rcnt = 0;
+    if (node.left && node.val === node.left.val) lcnt = lcnt + l + 1;
+    if (node.right && node.val === node.right.val) rcnt = rcnt + r + 1;
+    
+    res.max = Math.max(res.max, lcnt + rcnt);
+    
+    return Math.max(lcnt, rcnt);
+  }
+  /**
+   * Definition for a binary tree node.
+   * function TreeNode(val) {
+   *     this.val = val;
+   *     this.left = this.right = null;
+   * }
+   */
+  /**
+   * @param {TreeNode} root
+   * @return {number}
+   */
+  var longestUnivaluePath = function(root) {
+    const res = {
+      max: 0
+    };
+    helper(root, res);
+    return res.max;
+  };
+
+```
+
+### 其他优秀解答
+
+```
+暂无
+```

Diff for: daily/README.md

@@ -95,4 +95,9 @@ tag: `binary search` `math`
 tag: `logic`
 
 时间: 2019-07-01
+### [longest-univalue-path](./2019-07-04.md)
+
+tag:`recursive` `tree`
+
+时间: 2019-07-04