Merge pull request #915 from 0xff-dev/2096

Add solution and test-cases for problem 2096

Author: 6boris

leetcode/2001-2100/2096.Step-By-Step-Directions-From-a-Binary-Tree-Node-to-Another/README.md

@@ -1,28 +1,35 @@
 # [2096.Step-By-Step Directions From a Binary Tree Node to Another][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 the `root` of a **binary tree** with `n` nodes. Each node is uniquely assigned a value from `1` to `n`. You are also given an integer `startValue` representing the value of the start node `s`, and a different integer `destValue` representing the value of the destination node `t`.
+
+Find the **shortest path** starting from node `s` and ending at node `t`. Generate step-by-step directions of such path as a string consisting of only the **uppercase** letters `'L'`, `'R'`, and `'U'`. Each letter indicates a specific direction:
+
+- `'L'` means to go from a node to its **left child** node.
+- `'R'` means to go from a node to its **right child** node.
+- `'U`' means to go from a node to its **parent** node.
+
+Return the step-by-step directions of the **shortest path** from node `s` to node `t`.
 
-**Example 1:**
+**Example 1:**  
+
+![1](./eg1.png)
 
 ```
-Input: a = "11", b = "1"
-Output: "100"
+Input: root = [5,1,2,3,null,6,4], startValue = 3, destValue = 6
+Output: "UURL"
+Explanation: The shortest path is: 3 → 1 → 5 → 2 → 6.
 ```
 
-## 题意
-> ...
+**Example 2:**  
 
-## 题解
+![2](./eg2.png)
 
-### 思路1
-> ...
-Step-By-Step Directions From a Binary Tree Node to Another
-```go
 ```
-
+Input: root = [2,1], startValue = 2, destValue = 1
+Output: "L"
+Explanation: The shortest path is: 2 → 1.
+```
 
 ## 结语
 

leetcode/2001-2100/2096.Step-By-Step-Directions-From-a-Binary-Tree-Node-to-Another/Solution.go

@@ -1,5 +1,50 @@
 package Solution
 
-func Solution(x bool) bool {
-	return x
+type TreeNode struct {
+	Val         int
+	Left, Right *TreeNode
+}
+
+func Solution(root *TreeNode, startValue int, destValue int) string {
+	var dfs func(*TreeNode, *[]int, *[]byte, int) bool
+	dfs = func(tree *TreeNode, nums *[]int, dirs *[]byte, value int) bool {
+		if tree == nil {
+			return false
+		}
+		if tree.Val == value {
+			return true
+		}
+		if tree.Left != nil {
+			*nums = append(*nums, tree.Left.Val)
+			*dirs = append(*dirs, 'L')
+			if dfs(tree.Left, nums, dirs, value) {
+				return true
+			}
+			*nums = (*nums)[:len(*nums)-1]
+			*dirs = (*dirs)[:len(*dirs)-1]
+
+		}
+		if tree.Right != nil {
+			*nums = append(*nums, tree.Right.Val)
+			*dirs = append(*dirs, 'R')
+			if dfs(tree.Right, nums, dirs, value) {
+				return true
+			}
+			*nums = (*nums)[:len(*nums)-1]
+			*dirs = (*dirs)[:len(*dirs)-1]
+		}
+		return false
+	}
+	nums1, nums2 := []int{}, []int{}
+	dirs1, dirs2 := []byte{}, []byte{}
+	_ = dfs(root, &nums1, &dirs1, startValue)
+	_ = dfs(root, &nums2, &dirs2, destValue)
+
+	i := 0
+	for ; i < len(nums1) && i < len(nums2) && nums1[i] == nums2[i]; i++ {
+	}
+	for i1 := i; i1 < len(dirs1); i1++ {
+		dirs1[i1] = 'U'
+	}
+	return string(dirs1[i:]) + string(dirs2[i:])
 }

leetcode/2001-2100/2096.Step-By-Step-Directions-From-a-Binary-Tree-Node-to-Another/Solution_test.go

@@ -9,31 +9,42 @@ import (
 func TestSolution(t *testing.T) {
 	//	测试用例
 	cases := []struct {
-		name   string
-		inputs bool
-		expect bool
+		name        string
+		tree        *TreeNode
+		start, dest int
+		expect      string
 	}{
-		{"TestCase", true, true},
-		{"TestCase", true, true},
-		{"TestCase", false, false},
+		{"TestCase1", &TreeNode{
+			Val: 5,
+			Left: &TreeNode{
+				Val:  1,
+				Left: &TreeNode{Val: 3},
+			},
+			Right: &TreeNode{
+				Val:   2,
+				Left:  &TreeNode{Val: 6},
+				Right: &TreeNode{Val: 4},
+			},
+		}, 3, 6, "UURL"},
+		{"TestCase2", &TreeNode{Val: 2, Left: &TreeNode{Val: 1}}, 2, 1, "L"},
 	}
 
 	//	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.tree, c.start, c.dest)
 			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.tree, c.start, c.dest)
 			}
 		})
 	}
 }
 
-//	压力测试
+// 压力测试
 func BenchmarkSolution(b *testing.B) {
 }
 
-//	使用案列
+// 使用案列
 func ExampleSolution() {
 }