Create Step-By-Step Directions From a Binary Tree Node to Another.java

Author: varunu28

Medium/Step-By-Step Directions From a Binary Tree Node to Another.java

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+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode() {}
+ *     TreeNode(int val) { this.val = val; }
+ *     TreeNode(int val, TreeNode left, TreeNode right) {
+ *         this.val = val;
+ *         this.left = left;
+ *         this.right = right;
+ *     }
+ * }
+ */
+class Solution {
+  public String getDirections(TreeNode root, int startValue, int destValue) {
+    StringBuilder sourcePath = new StringBuilder();
+    StringBuilder destinationPath = new StringBuilder();
+    findPath(root, startValue, sourcePath);
+    findPath(root, destValue, destinationPath);
+    int idx = 0;
+    // Remove common prefix
+    while (idx < Math.min(sourcePath.length(), destinationPath.length()) && 
+           sourcePath.charAt(sourcePath.length() - idx - 1) == destinationPath.charAt(destinationPath.length() - idx - 1)) {
+      idx++;
+    }
+    // Replace remaining sourcePath with 'U' and append remaining destinationPath
+    return "U".repeat(sourcePath.length() - idx) + destinationPath.reverse().toString().substring(idx);
+  }
+  
+  private boolean findPath(TreeNode root, int value, StringBuilder sb) {
+    if (root.val == value) {
+      return true;
+    }
+    if (root.left != null && findPath(root.left, value, sb)) {
+      sb.append("L");
+    }
+    else if (root.right != null && findPath(root.right, value, sb)) {
+      sb.append("R");
+    }
+    return sb.length() > 0;
+  }
+}