Merge pull request #651 from 0xff-dev/2196

Add solution and test-cases for problem 2196

leetcode/2101-2200/2196.Create-Binary-Tree-From-Descriptions/README.md

@@ -1,28 +1,36 @@
 # [2196.Create Binary Tree From Descriptions][title]
 
-> [!WARNING|style:flat]
-> This question is temporarily unanswered if you have good ideas. Welcome to [Create Pull Request PR](https://github.com/kylesliu/awesome-golang-algorithm)
-
 ## Description
+You are given a 2D integer array `descriptions` where `descriptions[i] = [parenti, childi, isLefti]` indicates that `parenti` is the **parent** of `childi` in a **binary** tree of **unique** values. Furthermore,
+
+- If `isLefti == 1`, then `childi` is the left child of `parenti`.
+- If `isLefti == 0`, then `childi` is the right child of `parenti`.
+
+Construct the binary tree described by `descriptions` and return its **root**.
+
+The test cases will be generated such that the binary tree is **valid**.
 
-**Example 1:**
+**Example 1:**  
+
+![example1](./example1drawio.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: descriptions = [[20,15,1],[20,17,0],[50,20,1],[50,80,0],[80,19,1]]
+Output: [50,20,80,15,17,19]
+Explanation: The root node is the node with value 50 since it has no parent.
+The resulting binary tree is shown in the diagram.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![example2](./example2drawio.png)
 
-### 思路1
-> ...
-Create Binary Tree From Descriptions
-```go
 ```
-
+Input: descriptions = [[1,2,1],[2,3,0],[3,4,1]]
+Output: [1,2,null,null,3,4]
+Explanation: The root node is the node with value 1 since it has no parent.
+The resulting binary tree is shown in the diagram.
+```
 
 ## 结语
 

leetcode/2101-2200/2196.Create-Binary-Tree-From-Descriptions/Solution.go

@@ -1,5 +1,33 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+type TreeNode struct {
+	Val         int
+	Left, Right *TreeNode
+}
+
+func Solution(descriptions [][]int) *TreeNode {
+	indies := [100001]*TreeNode{}
+	children := [100001]bool{}
+	for _, desc := range descriptions {
+		parent, child, left := desc[0], desc[1], desc[2]
+		children[child] = true
+		if indies[parent] == nil {
+			indies[parent] = &TreeNode{Val: parent}
+		}
+		if indies[child] == nil {
+			indies[child] = &TreeNode{Val: child}
+		}
+		if left == 1 {
+			indies[parent].Left = indies[child]
+		} else {
+			indies[parent].Right = indies[child]
+		}
+	}
+	for _, desc := range descriptions {
+		if !children[desc[0]] {
+			return indies[desc[0]]
+		}
+	}
+
+	return nil
 }

leetcode/2101-2200/2196.Create-Binary-Tree-From-Descriptions/Solution_test.go

@@ -10,12 +10,35 @@ func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
 		name   string
-		inputs bool
-		expect bool
+		inputs [][]int
+		expect *TreeNode
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", [][]int{
+			{20, 15, 1}, {20, 17, 0}, {50, 20, 1}, {50, 80, 0}, {80, 19, 1},
+		}, &TreeNode{
+			Val: 50,
+			Left: &TreeNode{
+				Val:   20,
+				Left:  &TreeNode{Val: 15},
+				Right: &TreeNode{Val: 17},
+			},
+			Right: &TreeNode{
+				Val:  80,
+				Left: &TreeNode{Val: 19},
+			},
+		}},
+		{"TestCase2", [][]int{
+			{1, 2, 1}, {2, 3, 0}, {3, 4, 1},
+		}, &TreeNode{
+			Val: 1,
+			Left: &TreeNode{
+				Val: 2,
+				Right: &TreeNode{
+					Val:  3,
+					Left: &TreeNode{Val: 4},
+				},
+			},
+		}},
 	}
 
 	//	开始测试
@@ -30,10 +53,10 @@ func TestSolution(t *testing.T) {
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }