Sample code for implementing binary search tree in java

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java binary search tree example code

1.Left

2. Preorder traversal left, middle, right

3. Midorder traversal left, center, and left

4. Postorder traversal left, center, and left

public class BinaryTree {

  // 二叉树的根节点
  public TreeNode rootNode ;
  // 记录搜索深度
  public int count;

  /**
   * 利用传入一个数组来建立二叉树
   */
  public BinaryTree(int[] data) {
    for (int i = 0; i < data. length; i++) {
      addNodeToTree(data[i]);
    }
  }

  /**
   * 将指定的值加入到二叉树中适当的节点
   */
  private void addNodeToTree(int value) {
    TreeNode currentNode = rootNode;
    // 建立树根
    if (rootNode == null) {
      rootNode = new TreeNode(value);
      return;
    }

    // 建立二叉树
    while (true) {
      // 新增的value比节点的value小，则在左子树
      if (value < currentNode.value ) {
        if (currentNode.leftNode == null) {
          currentNode.leftNode = new TreeNode(value);
          return;
        } else {
          currentNode = currentNode.leftNode;
        }
      } else { // 新增的value比节点的value大，在右子树
        if (currentNode.rightNode == null) {
          currentNode. rightNode = new TreeNode(value);
          return;
        } else {
          currentNode = currentNode. rightNode;
        }
      }
    }
  }

  /**
   * 中序遍历(左子树 -树根- 右子树)
   */
  public void inOrder(TreeNode node) {
    if (node != null) {
      inOrder(node. leftNode);
      System. out.print("[" + node.value + "]");
      inOrder(node. rightNode);
    }
  }

  /**
   * 前序遍历(树根 -左子树- 右子树)
   */
  public void preOrder(TreeNode node) {
    if (node != null) {
      System. out.print("[" + node.value + "]");
      preOrder(node. leftNode);
      preOrder(node. rightNode);
    }
  }

  /**
   * 后序遍历(左子树 -右子树- 树根)
   */
  public void postOrder(TreeNode node) {
    if (node != null) {
      postOrder(node. leftNode);
      postOrder(node. rightNode);
      System. out.print("[" + node.value + "]");
    }
  }

  /**
   * 从二叉树中查找指定value
   */
  public boolean findTree(TreeNode node, int value) {
    if (node == null) {
      System. out.println("共搜索" + count + "次");
      return false;
    } else if (node.value == value) {
      System. out.println("共搜索" + count + "次");
      return true;
    } else if (value < node.value) {
      count++;
      return findTree(node.leftNode , value);
    } else {
      count++;
      return findTree(node.rightNode , value);
    }
  }

  /**
   * 利用中序遍历进行排序
   */
  public void sort() {
    this.inOrder(rootNode );
  }

  class TreeNode {
    int value ;
    TreeNode leftNode;
    TreeNode rightNode;

    public TreeNode(int value) {
      this.value = value;
      this.leftNode = null;
      this.rightNode = null;
    }
  }

  public static void main(String[] args) {
    int[] content = { 50, 35, 27, 45, 40, 48, 78, 56, 90 };

    BinaryTree tree = new BinaryTree(content);
    System. out.println("前序遍历:" );
    tree.preOrder(tree. rootNode);
    System. out.println("\n中序遍历:" );
    tree.inOrder(tree. rootNode);
    System. out.println("\n后序遍历:" );
    tree.postOrder(tree. rootNode);

    System. out.println("\n\n开始搜索:" );
    boolean isFind = tree.findTree(tree.rootNode, 48);
    System. out.println("是否搜索到" + 48 + ":" + isFind);

    System. out.println("\n进行排序:" );
    tree.sort();
  }
}

Pre-order traversal:

[50][35][27][45][40][48][78][56][90]

Mid-order traversal:

[27][35][40][45][48][50][56][78][90]

Post-order traversal:

[27][40][48][45][35][56][90][78][50]

Start search:

Searched 3 times in total

Whether 48 was found:true

Sort:

[27][35][40][45][48][50][56][78][90]

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