添加 problem 199

Algorithms/199. Binary Tree Right Side View/199. Binary Tree Right Side View.go

@@ -0,0 +1,41 @@
+package leetcode
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func rightSideView(root *TreeNode) []int {
+	if root == nil {
+		return []int{}
+	}
+	queue := []*TreeNode{}
+	queue = append(queue, root)
+	curNum, nextLevelNum, res, tmp := 1, 0, []int{}, []int{}
+	for len(queue) != 0 {
+		if curNum > 0 {
+			node := queue[0]
+			if node.Left != nil {
+				queue = append(queue, node.Left)
+				nextLevelNum++
+			}
+			if node.Right != nil {
+				queue = append(queue, node.Right)
+				nextLevelNum++
+			}
+			curNum--
+			tmp = append(tmp, node.Val)
+			queue = queue[1:]
+		}
+		if curNum == 0 {
+			res = append(res, tmp[len(tmp)-1])
+			curNum = nextLevelNum
+			nextLevelNum = 0
+			tmp = []int{}
+		}
+	}
+	return res
+}

Algorithms/199. Binary Tree Right Side View/199. Binary Tree Right Side View_test.go

@@ -0,0 +1,59 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question199 struct {
+	para199
+	ans199
+}
+
+// para 是参数
+// one 代表第一个参数
+type para199 struct {
+	one []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans199 struct {
+	one []int
+}
+
+func Test_Problem199(t *testing.T) {
+
+	qs := []question199{
+
+		question199{
+			para199{[]int{}},
+			ans199{[]int{}},
+		},
+
+		question199{
+			para199{[]int{1}},
+			ans199{[]int{1}},
+		},
+
+		question199{
+			para199{[]int{3, 9, 20, NULL, NULL, 15, 7}},
+			ans199{[]int{3, 20, 7}},
+		},
+
+		question199{
+			para199{[]int{1, 2, 3, 4, NULL, NULL, 5}},
+			ans199{[]int{1, 3, 5}},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 199------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans199, q.para199
+		fmt.Printf("【input】:%v      ", p)
+		root := Ints2TreeNode(p.one)
+		fmt.Printf("【output】:%v      \n", rightSideView(root))
+	}
+	fmt.Printf("\n\n\n")
+}

Algorithms/199. Binary Tree Right Side View/README.md

@@ -0,0 +1,29 @@
+# [199. Binary Tree Right Side View](https://leetcode.com/problems/binary-tree-right-side-view/)
+
+## 题目
+
+Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
+
+Example:
+
+```c
+Input: [1,2,3,null,5,null,4]
+Output: [1, 3, 4]
+Explanation:
+
+   1            <---
+ /   \
+2     3         <---
+ \     \
+  5     4       <---
+```
+
+ 
+
+## 题目大意
+
+这一题是按层序遍历的变种题。按照层序把每层的元素都遍历出来，然后依次取每一层的最右边的元素即可。用一个队列即可实现。
+
+第 102 题和第 107 题都是按层序遍历的。
+
+