java树结构遍历_树形结构,java_树遍历统计总数，树形结构,java - phpStudy

首先需要定义一个树结构的节点类，包含节点值和子节点列表：

class TreeNode {
    int val;
    List<TreeNode> children;
    public TreeNode(int val) {
        this.val = val;
        children = new ArrayList<>();
    }
}

然后可以实现树的遍历方法，比如先序遍历：

public void preOrder(TreeNode root) {
    if (root == null) {
        return;
    }
    System.out.print(root.val + " ");
    for (TreeNode child : root.children) {
        preOrder(child);
    }
}

统计树中节点总数可以使用递归方式，每个节点的子节点数目即为它的贡献，加上1就是以它为根的子树的总节点数：

public int countNodes(TreeNode root) {
    if (root == null) {
        return 0;
    }
    int count = 1;
    for (TreeNode child : root.children) {
        count += countNodes(child);
    }
    return count;
}

最后可以通过一个示例来测试：

public static void main(String[] args) {
    TreeNode root = new TreeNode(1);
    TreeNode node2 = new TreeNode(2);
    TreeNode node3 = new TreeNode(3);
    TreeNode node4 = new TreeNode(4);
    TreeNode node5 = new TreeNode(5);
    TreeNode node6 = new TreeNode(6);
    TreeNode node7 = new TreeNode(7);
    root.children.add(node2);
    root.children.add(node3);
    root.children.add(node4);
    node2.children.add(node5);
    node2.children.add(node6);
    node4.children.add(node7);
    System.out.print("Pre-order traversal: ");
    preOrder(root);
    System.out.println();
    System.out.println("Total number of nodes: " + countNodes(root));
}

输出结果：

Pre-order traversal: 1 2 5 6 3 4 7 
Total number of nodes: 7