add binary tree serialize and reconstruct way

src/class07/Code04_SerializeAndReconstructTree.java

@@ -2,9 +2,25 @@ package class07;
 
 import java.util.LinkedList;
 import java.util.Queue;
+import java.util.Stack;
 
 public class Code04_SerializeAndReconstructTree {
-
+    /*
+     * 二叉树可以通过先序、后序或者按层遍历的方式序列化和反序列化，
+     * 以下代码全部实现了。
+     * 但是，二叉树无法通过中序遍历的方式实现序列化和反序列化
+     * 因为不同的两棵树，可能得到同样的中序序列，即便补了空位置也可能一样。
+     * 比如如下两棵树
+     *         __2
+     *        /
+     *       1
+     *       和
+     *       1__
+     *          \
+     *           2
+     * 补足空位置的中序遍历结果都是{ null, 1, null, 2, null}
+     *       
+     * */
 	public static class Node {
 		public int value;
 		public Node left;
@@ -31,6 +47,38 @@ public class Code04_SerializeAndReconstructTree {
 		}
 	}
 
+	public static Queue<String> inSerial(Node head) {
+		Queue<String> ans = new LinkedList<>();
+		ins(head, ans);
+		return ans;
+	}
+
+	public static void ins(Node head, Queue<String> ans) {
+		if (head == null) {
+			ans.add(null);
+		} else {
+			ins(head.left, ans);
+			ans.add(String.valueOf(head.value));
+			ins(head.right, ans);
+		}
+	}
+
+	public static Queue<String> posSerial(Node head) {
+		Queue<String> ans = new LinkedList<>();
+		poss(head, ans);
+		return ans;
+	}
+
+	public static void poss(Node head, Queue<String> ans) {
+		if (head == null) {
+			ans.add(null);
+		} else {
+			poss(head.left, ans);
+			poss(head.right, ans);
+			ans.add(String.valueOf(head.value));
+		}
+	}
+
 	public static Node buildByPreQueue(Queue<String> prelist) {
 		if (prelist == null || prelist.size() == 0) {
 			return null;
@@ -49,6 +97,28 @@ public class Code04_SerializeAndReconstructTree {
 		return head;
 	}
 
+	public static Node buildByPosQueue(Queue<String> poslist) {
+		if (poslist == null || poslist.size() == 0) {
+			return null;
+		}
+		Stack<String> stack = new Stack<>();
+		while (!poslist.isEmpty()) {
+			stack.push(poslist.poll());
+		}
+		return posb(stack);
+	}
+
+	public static Node posb(Stack<String> posstack) {
+		String value = posstack.pop();
+		if (value == null) {
+			return null;
+		}
+		Node head = new Node(Integer.valueOf(value));
+		head.right = posb(posstack);
+		head.left = posb(posstack);
+		return head;
+	}
+
 	public static Queue<String> levelSerial(Node head) {
 		Queue<String> ans = new LinkedList<>();
 		if (head == null) {
@@ -140,20 +210,54 @@ public class Code04_SerializeAndReconstructTree {
 		return isSameValueStructure(head1.left, head2.left) && isSameValueStructure(head1.right, head2.right);
 	}
 
+	// for test
+	public static void printTree(Node head) {
+		System.out.println("Binary Tree:");
+		printInOrder(head, 0, "H", 17);
+		System.out.println();
+	}
+
+	public static void printInOrder(Node head, int height, String to, int len) {
+		if (head == null) {
+			return;
+		}
+		printInOrder(head.right, height + 1, "v", len);
+		String val = to + head.value + to;
+		int lenM = val.length();
+		int lenL = (len - lenM) / 2;
+		int lenR = len - lenM - lenL;
+		val = getSpace(lenL) + val + getSpace(lenR);
+		System.out.println(getSpace(height * len) + val);
+		printInOrder(head.left, height + 1, "^", len);
+	}
+
+	public static String getSpace(int num) {
+		String space = " ";
+		StringBuffer buf = new StringBuffer("");
+		for (int i = 0; i < num; i++) {
+			buf.append(space);
+		}
+		return buf.toString();
+	}
+
 	public static void main(String[] args) {
 		int maxLevel = 5;
 		int maxValue = 100;
 		int testTimes = 1000000;
+		System.out.println("test begin");
 		for (int i = 0; i < testTimes; i++) {
 			Node head = generateRandomBST(maxLevel, maxValue);
 			Queue<String> pre = preSerial(head);
+			Queue<String> pos = posSerial(head);
 			Queue<String> level = levelSerial(head);
 			Node preBuild = buildByPreQueue(pre);
+			Node posBuild = buildByPosQueue(pos);
 			Node levelBuild = buildByLevelQueue(level);
-			if (!isSameValueStructure(preBuild, levelBuild)) {
+			if (!isSameValueStructure(preBuild, posBuild) || !isSameValueStructure(posBuild, levelBuild)) {
 				System.out.println("Oops!");
 			}
 		}
-		System.out.println("finish!");
+		System.out.println("test finish!");
+		
 	}
 }