Question

您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);
}
}

当前输出是7 2 6 4但我希望它们在可能的情况下被添加到系统输出中的总和中。我不能因为某些原因让它工作，所以也许有人可以帮助我。

Answer 1

您需要返回左右节点的总和，并从main()打印返回值。此外，由于您传入sum()，因此root无需成为一种intance方法：

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获取总和：

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

2 个答案: