Create Solution2.java

Author: yanglbme

solution/2000-2099/2096.Step-By-Step Directions From a Binary Tree Node to Another/Solution2.java

@@ -0,0 +1,63 @@
+/**
+ * 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 {
+    static byte[] path = new byte[200_001];
+    int strtLevel = -1;
+    int destLevel = -1;
+    int comnLevel = -1;
+
+    public String getDirections(TreeNode root, int startValue, int destValue) {
+        findPaths(root, startValue, destValue, 100_000);
+        int answerIdx = comnLevel;
+        for (int i = strtLevel; i > comnLevel; i--) {
+            path[--answerIdx] = 'U';
+        }
+        return new String(path, answerIdx, destLevel - answerIdx);
+    }
+
+    private int findPaths(TreeNode node, int strtVal, int destVal, int level) {
+        if (node == null) {
+            return 0;
+        }
+        int result = 0;
+        if (node.val == strtVal) {
+            strtLevel = level;
+            result = 1;
+        } else if (node.val == destVal) {
+            destLevel = level;
+            result = 1;
+        }
+        int leftFound = 0;
+        int rightFound = 0;
+        if (comnLevel < 0) {
+            if (destLevel < 0) {
+                path[level] = 'L';
+            }
+            leftFound = findPaths(node.left, strtVal, destVal, level + 1);
+            rightFound = 0;
+            if (comnLevel < 0) {
+                if (destLevel < 0) {
+                    path[level] = 'R';
+                }
+                rightFound = findPaths(node.right, strtVal, destVal, level + 1);
+            }
+        }
+        if (comnLevel < 0 && leftFound + rightFound + result == 2) {
+            comnLevel = level;
+        }
+        return result | leftFound | rightFound;
+    }
+}