Create Solution.go

Author: yanglbme

solution/2000-2099/2096.Step-By-Step Directions From a Binary Tree Node to Another/Solution.go

@@ -0,0 +1,51 @@
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func getDirections(root *TreeNode, startValue int, destValue int) string {
+	var lca func(node *TreeNode, p, q int) *TreeNode
+	lca = func(node *TreeNode, p, q int) *TreeNode {
+		if node == nil || node.Val == p || node.Val == q {
+			return node
+		}
+		left := lca(node.Left, p, q)
+		right := lca(node.Right, p, q)
+		if left != nil && right != nil {
+			return node
+		}
+		if left != nil {
+			return left
+		}
+		return right
+	}
+	var dfs func(node *TreeNode, x int, path *[]byte) bool
+	dfs = func(node *TreeNode, x int, path *[]byte) bool {
+		if node == nil {
+			return false
+		}
+		if node.Val == x {
+			return true
+		}
+		*path = append(*path, 'L')
+		if dfs(node.Left, x, path) {
+			return true
+		}
+		(*path)[len(*path)-1] = 'R'
+		if dfs(node.Right, x, path) {
+			return true
+		}
+		*path = (*path)[:len(*path)-1]
+		return false
+	}
+
+	node := lca(root, startValue, destValue)
+	pathToStart := []byte{}
+	pathToDest := []byte{}
+	dfs(node, startValue, &pathToStart)
+	dfs(node, destValue, &pathToDest)
+	return string(bytes.Repeat([]byte{'U'}, len(pathToStart))) + string(pathToDest)
+}