树结构练习

Posted 2020-09-17 it_worker365

import java.util.ArrayList;
import java.util.List;
import java.util.Queue;
import java.util.concurrent.LinkedBlockingQueue;

/**
 * Created by itworker365 on 5/10/2017.
 */
public class BinaryTree {
    public static void main (String[] args) {
        List<Integer> list = new ArrayList<Integer>();
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);
        list.add(5);
        list.add(6);
        list.add(7);

        BinaryTree bt = new BinaryTree();
        TreeNode tree = bt.buildTreeAsList(list, null, 0);
        bt.printTreeLevelTrace(tree);
    }
    /**
     * 按照LIST顺序构建完全二叉树
     * */
    public TreeNode buildTreeAsList (List<Integer> list, TreeNode root, int pos) {
        if (root == null) {
            root = new TreeNode(list.get(0), null, null);
        }
        int listSize = list.size();
        int leftPos = pos * 2 + 1;
        int rightPos = pos * 2 + 2;
        if (pos == listSize) {
            return root;
        } else {
            // build left
            if (leftPos < listSize) {
                TreeNode nodeLeft = new TreeNode(list.get(leftPos), null, null);
                root.setLeft(nodeLeft);
                buildTreeAsList(list, nodeLeft, leftPos);
            }
            // build right
            if (rightPos < listSize){
                TreeNode nodeRight = new TreeNode(list.get(rightPos), null, null);
                root.setRight(nodeRight);
                buildTreeAsList(list, nodeRight, rightPos);
            }
        }
        return root;
    }
    // 前序遍历， 根-》左-》右
    private void printTreePreOrderRec (TreeNode root) {
        if (root != null) {
            System.out.println(root.value);
            printTreePreOrderRec(root.getLeft());
            printTreePreOrderRec(root.getRight());
        }
    }

    // 中序遍历， 左-》根-》右
    private void printTreeMidOrderRec (TreeNode root) {
        if (root != null) {
            printTreeMidOrderRec(root.getLeft());
            System.out.println(root.value);
            printTreeMidOrderRec(root.getRight());
        }
    }

    // 后序遍历， 左-》右-》根
    private void printTreePostOrderRec (TreeNode root) {
        if (root != null) {
            printTreePostOrderRec(root.getLeft());
            printTreePostOrderRec(root.getRight());
            System.out.println(root.value);
        }
    }

    // 层序遍历
    private void printTreeLevelTrace (TreeNode root) {
        Queue<TreeNode> queue = new LinkedBlockingQueue<>();
        if (root == null) {
            return;
        }
        queue.add(root);
        while (!queue.isEmpty()) {
            TreeNode node = queue.poll();
            System.out.println(node.getValue());
            if (node.getLeft() != null) {
                queue.offer(node.getLeft());
            }
            if (node.getRight() != null) {
                queue.offer(node.getRight());
            }
        }
    }

    //  只打印叶子结点
    private void printTreeLefeRec (TreeNode root) {
        if (root.getLeft() == null || root.getRight() == null) {
            System.out.println(root.getValue());
        } else {
            printTreeMidOrderRec(root.getLeft());
            printTreeMidOrderRec(root.getRight());
        }
    }
    static class TreeNode {
        int value;
        TreeNode left;
        TreeNode right;

        public TreeNode(int value, TreeNode left, TreeNode right) {
            this.value = value;
            this.left = left;
            this.right = right;
        }

        public int getValue() {
            return value;
        }

        public void setValue(int value) {
            this.value = value;
        }

        public TreeNode getLeft() {
            return left;
        }

        public void setLeft(TreeNode left) {
            this.left = left;
        }

        public TreeNode getRight() {
            return right;
        }

        public void setRight(TreeNode right) {
            this.right = right;
        }
    }
}