Update solution 0058、0551、0958

leetcode/0958.Check-Completeness-of-a-Binary-Tree/0958.Check Completeness of a Binary Tree.go

@@ -17,9 +17,7 @@ type TreeNode = structures.TreeNode
  */
 
 func isCompleteTree(root *TreeNode) bool {
-	queue := []*TreeNode{root}
-	found := false
-
+	queue, found := []*TreeNode{root}, false
 	for len(queue) > 0 {
 		node := queue[0] //取出每一层的第一个节点
 		queue = queue[1:]
@@ -34,4 +32,4 @@ func isCompleteTree(root *TreeNode) bool {
 		}
 	}
 	return true
-}
+}

leetcode/0958.Check-Completeness-of-a-Binary-Tree/README.md

@@ -1,53 +1,89 @@
 # [958. Check Completeness of a Binary Tree](https://leetcode.com/problems/check-completeness-of-a-binary-tree/)
 
+
 ## 题目
 
-Given the root of a binary tree, determine if it is a complete binary tree.
+Given the `root` of a binary tree, determine if it is a *complete binary tree*.
 
-In a complete binary tree, every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between 1 and 2h nodes inclusive at the last level h.
+In a **[complete binary tree](http://en.wikipedia.org/wiki/Binary_tree#Types_of_binary_trees)**, every level, except possibly the last, is completely filled, and all nodes in the last level are as far left as possible. It can have between `1` and `2h` nodes inclusive at the last level `h`.
 
-Example 1:
-```c
+**Example 1:**
+
+![https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-1.png](https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-1.png)
+
+```
 Input: root = [1,2,3,4,5,6]
 Output: true
 Explanation: Every level before the last is full (ie. levels with node-values {1} and {2, 3}), and all nodes in the last level ({4, 5, 6}) are as far left as possible.
 
-     1
-   /   \
-  2     3 
- / \   /
-4   5 6    
 ```
-Example 2:
-```c
+
+**Example 2:**
+
+![https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-2.png](https://assets.leetcode.com/uploads/2018/12/15/complete-binary-tree-2.png)
+
+```
 Input: root = [1,2,3,4,5,null,7]
 Output: false
 Explanation: The node with value 7 isn't as far left as possible.
 
-     1
-   /   \
-  2     3 
- / \     \
-4   5     7
 ```
 
-Constraints:
-
-The number of nodes in the tree is in the range [1, 100].
-1 <= Node.val <= 1000
+**Constraints:**
 
+- The number of nodes in the tree is in the range `[1, 100]`.
+- `1 <= Node.val <= 1000`
 
 ## 题目大意
 
+给定一个二叉树，确定它是否是一个完全二叉树。
+
+百度百科中对完全二叉树的定义如下：
+
 若设二叉树的深度为 h，除第 h 层外，其它各层 (1～h-1) 的结点数都达到最大个数，第 h 层所有的结点都连续集中在最左边，这就是完全二叉树。（注：第 h 层可能包含 1~ 2h 个节点。）
 
-说明要判断每个节点的左孩子必须不为空。
-
-
 ## 解题思路
 
 - 这一题是按层序遍历的变种题。
 - 判断每个节点的左孩子是否为空。
-- 第 102,107,199 都是按层序遍历的。
+- 类似的题目，第 102，107，199 题都是按层序遍历的。
 
+## 代码
 
+```go
+package leetcode
+
+import (
+	"github.com/halfrost/LeetCode-Go/structures"
+)
+
+// TreeNode define
+type TreeNode = structures.TreeNode
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+
+func isCompleteTree(root *TreeNode) bool {
+	queue, found := []*TreeNode{root}, false
+	for len(queue) > 0 {
+		node := queue[0] //取出每一层的第一个节点
+		queue = queue[1:]
+		if node == nil {
+			found = true
+		} else {
+			if found {
+				return false // 层序遍历中，两个不为空的节点中出现一个 nil
+			}
+			//如果左孩子为nil，则append进去的node.Left为nil
+			queue = append(queue, node.Left, node.Right)
+		}
+	}
+	return true
+}
+```