Java怎么生成树形结构数据

Java中生成树形结构数据可以使用多种方法，下面列举了两种常用的方法：

方法一：使用递归实现

class TreeNode {
    int val;
    List children;

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

public class TreeGenerator {
    public static TreeNode generateTree(int[] nums, int rootIndex) {
        if (rootIndex >= nums.length) {
            return null;
        }
        
        TreeNode root = new TreeNode(nums[rootIndex]);
        
        int leftChildIndex = 2 * rootIndex + 1;
        int rightChildIndex = 2 * rootIndex + 2;
        
        root.children.add(generateTree(nums, leftChildIndex));
        root.children.add(generateTree(nums, rightChildIndex));
        
        return root;
    }
    
    public static void main(String[] args) {
        int[] nums = {1, 2, 3, 4, 5, 6, 7};
        
        TreeNode root = generateTree(nums, 0);
        
        // 打印树的结构
        printTree(root, 0);
    }
    
    public static void printTree(TreeNode root, int level) {
        if (root == null) {
            return;
        }
        
        for (int i = 0; i < level; i++) {
            System.out.print("\t");
        }
        
        System.out.println(root.val);
        
        for (TreeNode child : root.children) {
            printTree(child, level + 1);
        }
    }
}

方法二：使用队列实现

class TreeNode {
    int val;
    List children;

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

public class TreeGenerator {
    public static TreeNode generateTree(int[] nums) {
        if (nums.length == 0) {
            return null;
        }
        
        TreeNode root = new TreeNode(nums[0]);
        Queue queue = new LinkedList<>();
        queue.offer(root);
        
        int index = 1;
        while (!queue.isEmpty() && index < nums.length) {
            TreeNode currNode = queue.poll();
            
            // 左孩子
            if (index < nums.length) {
                TreeNode leftChild = new TreeNode(nums[index++]);
                currNode.children.add(leftChild);
                queue.offer(leftChild);
            }
            
            // 右孩子
            if (index < nums.length) {
                TreeNode rightChild = new TreeNode(nums[index++]);
                currNode.children.add(rightChild);
                queue.offer(rightChild);
            }
        }
        
        return root;
    }
    
    public static void main(String[] args) {
        int[] nums = {1, 2, 3, 4, 5, 6, 7};
        
        TreeNode root = generateTree(nums);
        
        // 打印树的结构
        printTree(root, 0);
    }
    
    public static void printTree(TreeNode root, int level) {
        if (root == null) {
            return;
        }
        
        for (int i = 0; i < level; i++) {
            System.out.print("\t");
        }
        
        System.out.println(root.val);
        
        for (TreeNode child : root.children) {
            printTree(child, level + 1);
        }
    }
}

以上两种方法都可以根据给定的数组生成树形结构数据，并且可以通过递归或者队列的方式进行遍历和打印。