获取二叉树第n层的节点个数_java写二叉树的获取n层个结点-优快云博客

本文链接：https://blog.youkuaiyun.com/dream328/article/details/12851685

本文介绍了一个简单的Java程序，该程序能够创建一个二叉树，并计算出指定层的节点数量。通过递归的方式，算法可以有效地遍历二叉树的每一层，最终得到目标层数的节点总数。

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import java.util.Scanner;

/**
 * 求二叉树第n层节点个数
 * 
 */
public class GetBinaryTreeLevelN {

  static class TreeNode {
    public int value;
    public TreeNode left;
    public TreeNode right;
  }

  public static void createTree(TreeNode root) {
    if (root == null) {
      return;
    }
    System.out.println("输入" + root.value + "左右儿子的值：");
    Scanner in = new Scanner(System.in);
    int left = in.nextInt();
    int right = in.nextInt();
    if (left == 0) {
      root.left = null;
    } else {
      TreeNode leftChild = new TreeNode();
      leftChild.value = left;
      root.left = leftChild;
    }
    if (right == 0) {
      root.right = null;
    } else {
      TreeNode rightChild = new TreeNode();
      rightChild.value = right;
      root.right = rightChild;
    }
    createTree(root.left);
    createTree(root.right);
  }

  public static int getNumInLevel(TreeNode root, int n) {
    if (root == null || n <= 0)
      return 0;
    if (n == 1) {
      return root == null ? 0 : 1;
    }
    int left = getNumInLevel(root.left, n - 1);
    int right = getNumInLevel(root.right, n - 1);

    return left + right;
  }

  public static void main(String[] args) {
    // TODO Auto-generated method stub
    TreeNode root = new TreeNode();
    root.value = 0;
    createTree(root);
    System.out.print("节点个数为：" + getNumInLevel(root, 3));
  }

}