updayte

hard/297.serialize-and-deserialize-binary-tree.java

@@ -0,0 +1,66 @@
+import java.util.LinkedList;
+
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+public class Codec {
+
+    // Encodes a tree to a single string.
+    public String serialize(TreeNode root) {
+        StringBuilder sb = new StringBuilder();
+		LinkedList<TreeNode> list = new LinkedList<TreeNode>();
+		list.add(root);
+		TreeNode curr;
+		while (!list.isEmpty()) {
+			curr = list.poll();
+			if (curr == null) {
+				sb.append("null,");
+				continue;
+			}
+			sb.append(curr.val);
+			sb.append(',');
+			list.add(curr.left);
+			list.add(curr.right);
+		}
+		sb.deleteCharAt(sb.length()-1);
+		return sb.toString();
+    }
+
+    // Decodes your encoded data to tree.
+    public TreeNode deserialize(String data) {
+		String[] strs = data.split(",");
+		if (strs[0].equals("null")) return null;
+		TreeNode root = new TreeNode(Integer.parseInt(strs[0]));
+		LinkedList<TreeNode> list = new LinkedList<TreeNode>();
+		list.add(root);
+		int idx = 1;
+		while (!list.isEmpty()) {
+			TreeNode curr = list.poll();
+			if (idx < strs.length) {
+				if (!strs[idx].equals("null")) {
+					curr.left = new TreeNode(Integer.parseInt(strs[idx]));
+					list.add(curr.left);
+				}
+				idx++;
+			}
+			if (idx < strs.length) {
+				if (!strs[idx].equals("null")) {
+					curr.right = new TreeNode(Integer.parseInt(strs[idx]));
+					list.add(curr.right);
+				}
+				idx++;
+			}
+		}
+        return root;
+    }
+}
+
+// Your Codec object will be instantiated and called as such:
+// Codec codec = new Codec();
+// codec.deserialize(codec.serialize(root));