Merge pull request 6boris#427 from 0xff-dev/1361

Add solution and test-cases for problem 1361

Author: 6boris

leetcode/1301-1400/1361.Validate-Binary-Tree-Nodes/1503_ex1.png

@@ -1,28 +1,39 @@
 # [1361.Validate Binary Tree Nodes][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 have `n` binary tree nodes numbered from `0` to `n - 1` where node `i` has two children `leftChild[i]` and `rightChild[i]`, return `true` if and only if **all** the given nodes form **exactly one** valid binary tree.
+
+If node `i` has no left child then `leftChild[i]` will equal `-1`, similarly for the right child.
+
+Note that the nodes have no values and that we only use the node numbers in this problem.
 
-**Example 1:**
+**Example 1:**  
+
+![example1](./1503_ex1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: n = 4, leftChild = [1,-1,3,-1], rightChild = [2,-1,-1,-1]
+Output: true
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![example2](./1503_ex2.png)
 
-### 思路1
-> ...
-Validate Binary Tree Nodes
-```go
+```
+Input: n = 4, leftChild = [1,-1,3,-1], rightChild = [2,3,-1,-1]
+Output: false
 ```
 
+**Example 3:**  
+
+![example3](./1503_ex3.png)
+
+
+```
+Input: n = 2, leftChild = [1,0], rightChild = [-1,-1]
+Output: false
+```
 
 ## 结语
 

leetcode/1301-1400/1361.Validate-Binary-Tree-Nodes/1503_ex2.png

@@ -1,5 +1,54 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+func Solution(n int, leftChild []int, rightChild []int) bool {
+
+	father := make([]int, n)
+	for i := 0; i < n; i++ {
+		// 孤立的节点
+		father[i] = i
+	}
+
+	for node := 0; node < n; node++ {
+		left := leftChild[node]
+		if left != -1 {
+			lf := father[left]
+			if lf != left && lf != node || left == father[node] {
+				return false
+			}
+			father[left] = node
+		}
+		right := rightChild[node]
+		if right != -1 {
+			rf := father[right]
+			if rf != right && rf != node || right == father[node] {
+				return false
+			}
+			father[right] = node
+		}
+	}
+	/*
+			0
+		1       2
+		0 1 2
+	*/
+	sameFather := -1
+	for node := 0; node < n; node++ {
+		steps := 0
+		walkerNode := node
+		nodeFather := father[walkerNode]
+		for nodeFather != walkerNode && steps <= n {
+			walkerNode = nodeFather
+			nodeFather = father[walkerNode]
+			steps++
+		}
+		if steps > n {
+			return false
+		}
+		if sameFather != -1 && nodeFather != sameFather {
+			return false
+		}
+		sameFather = nodeFather
+	}
+
+	return true
 }

leetcode/1301-1400/1361.Validate-Binary-Tree-Nodes/1503_ex3.png

@@ -9,31 +9,32 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name        string
+		n           int
+		left, right []int
+		expect      bool
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", 4, []int{1, -1, 3, -1}, []int{2, -1, -1, -1}, true},
+		{"TestCase2", 4, []int{1, -1, 3, -1}, []int{2, 3, -1, -1}, false},
+		{"TestCase3", 2, []int{1, 0}, []int{-1, -1}, false},
 	}
 
 	//	开始测试
 	for i, c := range cases {
 		t.Run(c.name+" "+strconv.Itoa(i), func(t *testing.T) {
-			got := Solution(c.inputs)
+			got := Solution(c.n, c.left, c.right)
 			if !reflect.DeepEqual(got, c.expect) {
-				t.Fatalf("expected: %v, but got: %v, with inputs: %v",
-					c.expect, got, c.inputs)
+				t.Fatalf("expected: %v, but got: %v, with inputs: %v %v %v",
+					c.expect, got, c.n, c.left, c.right)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }