二叉树输出

Question

嗨，我如何让程序输出数字的总和而不是单独给出它们？

public class Tree {
private Node root;
public int sum;

public class Node{
    private Node left;
    private Node right;
    private int val;

    public Node(int data) {
        this.val = data;
    }
}

public void createTree() {
    Node first = new Node(7);
    Node second = new Node(2);
    Node third = new Node(6);
    Node fourth = new Node(4);


    root = first;
    first.left = second;
    first.right = third;

    second.left = fourth;

}

public void Sum(Node root) {
    if(root == null) {
        return;
    }
    System.out.print(root.val + " ");
    Sum(root.left);
    Sum(root.right);
}

public static void main(String[] args) {
    Tree tree = new Tree();
    tree.createTree();
    tree.Sum(tree.root);
}
}

当前输出为 7 2 6 4 但我希望尽可能将它们添加到系统输出中的总和中。由于某种原因我无法让它工作所以也许有人可以帮助我。

Answer 1

您需要return左右节点的总和，并打印main()的return值。此外，sum() 不需要成为实例方法，因为您要传入 root:

public static int sum(Node root) {
    if(root == null) {
        return 0;
    }
    return sum(root.left) + sum(root.right);
}

public static void main(String[] args) {
    Tree tree = new Tree();
    tree.createTree();
    System.out.println(sum(tree.root));
}

Answer 2

您可以通过执行以下操作递归地获得总和：

public double sum(Node root) {      
  double leftSum, rightSum, totalSum;

  if (root == null) {
   totalSum = 0;
   return totalSum;
  }else {
   leftSum = sum(root.left);
   rightSum = sum(root.right);
   totalSum = root.val + leftSum + rightSum;
   return totalSum;
  }
}

二叉树输出

Binary Tree Output

java

binary-tree