大话数据结构—二叉树（十）

1.二叉树3种递归遍历

public class Tree {
    // 前序遍历
    public static void preOrderSearch(Node root) {
        if (root == null) {
            return;
        }
        System.out.print(root.data);
        preOrderSearch(root.left);
        preOrderSearch(root.right);
    }

    // 中序遍历
    static public void midOrderSearch(Node root) {
        if (root == null) {
            return;
        }
        midOrderSearch(root.left);
        System.out.print(root.data);
        midOrderSearch(root.right);
    }

    // 后序遍历
    public static void postOrderSearch(Node root) {
        if (root == null) {
            return;
        }
        postOrderSearch(root.left);
        postOrderSearch(root.right);
        System.out.print(root.data);
    }

    static class Node {
        Object data;
        Node left;
        Node right;

        public Node(Object data) {
            this.data = data;
        }
    }

    public static void main(String[] args) {
        Node node = new Node(0);
        Node node1 = new Node(1);
        Node node2 = new Node(2);
        Node node3 = new Node(3);
        Node node4 = new Node(4);

        node.left = node1;
        node.right = node2;
        node1.left = node3;
        node1.right = node4;

        Tree tree = new Tree();
        tree.preOrderSearch(node);
        System.out.println("-----------");
        tree.midOrderSearch(node);
        System.out.println("-----------");
        tree.postOrderSearch(node);

    }
}

2.层级遍历

public class LevelTravel {

    public static void main(String[] args) {
        Node root = new Node(10);
        Node left = new Node(4);
        Node right = new Node(7);
        Node node1 = new Node(3);
        Node node2 = new Node(6);
        root.left = left;
        root.right = right;
        left.left = node1;
        left.right = node2;

        search(root);

    }

    public static void search(Node root) {
        if (root == null) {
            return;
        }
        LinkedList<Node> queue = new LinkedList<>();
        queue.offer(root);
        while (!queue.isEmpty()) {
            Node temp = queue.poll();
            System.out.println(temp.data);
            if (temp.left != null) {
                queue.offer(temp.left);
            }
            if (temp.right != null) {
                queue.offer(temp.right);
            }
        }
    }


    static class Node {
        Node left;
        Node right;
        Object data;

        public Node(Object data) {
            this.data = data;
        }
    }

}

引用原文：https://www.cnblogs.com/llguanli/p/7363657.html