DaleStudy#288 Serialize and Deserialize Binary Tree

Author: forest000014

serialize-and-deserialize-binary-tree/forest000014.java

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+/*
+# Time Complexity: O(n)
+# Space Complexity: O(n)
+*/
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+public class Codec {
+
+    static int idx;
+
+    // Encodes a tree to a single string.
+    public String serialize(TreeNode root) {
+        if (root == null) return "";
+
+        return dfs(root);
+    }
+
+    private String dfs(TreeNode curr) {
+        if (curr == null) {
+            return ".";
+        }
+
+        return curr.val + "," + dfs(curr.left) + "," + dfs(curr.right);
+    }
+
+    // Decodes your encoded data to tree.
+    public TreeNode deserialize(String data) {
+        if ("".equals(data)) return null;
+
+        String[] values = data.split(",");
+
+        idx = 0;
+        return dfs2(values);
+    }
+
+    private TreeNode dfs2(String[] values) {
+        if (".".equals(values[idx])) {
+            idx++;
+            return null;
+        }
+
+        TreeNode curr = new TreeNode(Integer.parseInt(values[idx]));
+        idx++;
+        curr.left = dfs2(values);
+        curr.right = dfs2(values);
+
+        return curr;
+    }
+}
+
+// Your Codec object will be instantiated and called as such:
+// Codec ser = new Codec();
+// Codec deser = new Codec();
+// TreeNode ans = deser.deserialize(ser.serialize(root));