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BinaryTree.java
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181 lines (169 loc) · 5.41 KB
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package Algorithm.Tree;
import java.lang.reflect.Array;
import java.util.ArrayDeque;
import java.util.ArrayList;
/**
* Created by lenovo on 2017/4/1.
*/
public class BinaryTree {
public TreeNode root;
public void visit(TreeNode node) {
System.out.print(node.val + ",");
}
public BinaryTree(TreeNode root) {
this.root = root;
}
public TreeNode init(String data) {
//将字符串形如"1,2,3,#,#,4,5"转化为二叉树，即反序列化,#代表空节点
if (data == null)
return null;
String[] vals = data.split(",");
ArrayList<TreeNode> queue = new ArrayList<>();
TreeNode root = new TreeNode(Integer.parseInt(vals[0]));
queue.add(root);
int index = 0;//index in queue
boolean isLeftChild = true;
for (int i = 1; i < vals.length; i++) {
if (!vals[i].equals("#")) {
TreeNode node = new TreeNode(Integer.parseInt(vals[i]));
if (isLeftChild) {
queue.get(index).left = node;
} else {
queue.get(index).right = node;
}
queue.add(node);
}
if (!isLeftChild) {
index++;
}
isLeftChild = !isLeftChild;
}
return root;
}
public String Serialize(TreeNode root) {
if (root == null) {
return null;
}
StringBuilder sb = new StringBuilder();
ArrayList<TreeNode> queue = new ArrayList<>();
queue.add(root);
for (int i = 0; i < queue.size(); i++) {
TreeNode node = queue.get(i);
if (node == null)
continue;
queue.add(node.left);
queue.add(node.right);
}
for (int i = 0; i < queue.size(); i++) {
if (queue.get(i) == null)
sb.append("#,");
else
sb.append("," + queue.get(i));
}
return sb.toString();
}
public TreeNode getParentRecursively(TreeNode root, TreeNode node) {
// 非递归实现查找某节点的父节点
root = this.root;//从树的根结点开始找
TreeNode temp;
if (root == null) {
return null;
}
if (node == root.left || node == root.right) {
return root;
}
if ((temp = getParentRecursively(root.left, node)) != null) {
return temp;
}
if ((temp = getParentRecursively(root.right, node)) != null) {
return temp;
}
return null;
}
public TreeNode getParentLooply(TreeNode node) {
ArrayDeque<TreeNode> stack = new ArrayDeque<>();
TreeNode currentRoot = this.root;
stack.push(null);
while (currentRoot != null) {
if (node == currentRoot.left || node == currentRoot.right) {
return currentRoot;
}
if (currentRoot.right != null) {
stack.push(currentRoot.right);
}
if (currentRoot.left != null) {
currentRoot = currentRoot.left;
} else {
currentRoot = stack.pop();
}
}
return null;
}
public void traversalRecursively(TreeNode root) {
if (root != null) {
//visit(root);this is preorder
traversalRecursively(root.left);
// visit(root);this is inorder
traversalRecursively(root.right);
// visit(root);this is postoder
}
}
public ArrayList<Integer> preOrder() {
ArrayList<Integer> preOrder = new ArrayList<>();
ArrayDeque<TreeNode> stack = new ArrayDeque<>();
if (root == null)
return preOrder;
stack.push(root);
while (!stack.isEmpty()) {
TreeNode node = stack.pop();
preOrder.add(node.val);
if (node.right != null) {
stack.push(node.right);
}
if (node.left != null) {
stack.push(node.left);
}
}
return preOrder;
}
public ArrayList<Integer> inOrder() {
ArrayList<Integer> inorder = new ArrayList<>();
ArrayDeque<TreeNode> stack = new ArrayDeque<>();
if (root == null) {
return inorder;
}
TreeNode ptr = root;
while (ptr != null || !stack.isEmpty()) {
while (ptr != null) {
stack.push(ptr);
ptr = ptr.left;
}
ptr = stack.pop();
inorder.add(ptr.val);
ptr = ptr.right;
}
return inorder;
}
public ArrayList<ArrayList<Integer>> levelOrder(TreeNode root) {
// write your code here
ArrayList<ArrayList<Integer>> res = new ArrayList<>();
ArrayDeque<TreeNode> queue = new ArrayDeque<>();
if (root == null)
return res;
queue.offer(root);
while (!queue.isEmpty()) {
ArrayList<Integer> level = new ArrayList<>();
int size = queue.size();
for (int i = 0; i < size; i++) {
TreeNode node = queue.poll();
level.add(node.val);
if (node.left != null)
queue.offer(node.left);
if (node.right != null)
queue.offer(node.right);
}
res.add(level);
}
return res;
}
}