Merge pull request #168 from 3inchtime/958

add solution - 958

Author: halfrost

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

@@ -0,0 +1,37 @@
+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 := []*TreeNode{root}
+	found := 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
+}

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

@@ -0,0 +1,51 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/halfrost/LeetCode-Go/structures"
+)
+
+type question958 struct {
+	para958
+	ans958
+}
+
+// para 是参数
+// one 代表第一个参数
+type para958 struct {
+	one []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans958 struct {
+	one bool
+}
+
+func Test_Problem958(t *testing.T) {
+
+	qs := []question958{
+
+		{
+			para958{[]int{1, 2, 3, 4, 5, 6}},
+			ans958{true},
+		},
+
+		{
+			para958{[]int{1, 2, 3, 4, 5, structures.NULL, 7}},
+			ans958{false},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 958------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans958, q.para958
+		fmt.Printf("【input】:%v      ", p)
+		root := structures.Ints2TreeNode(p.one)
+		fmt.Printf("【output】:%v      \n", isCompleteTree(root))
+	}
+	fmt.Printf("\n\n\n")
+}

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

@@ -0,0 +1,53 @@
+# [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.
+
+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.
+
+Example 1:
+```c
+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
+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
+
+
+## 题目大意
+
+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。
+
+