二叉树遍历--深度优先及广度优先

public class BinaryTree {
    static class TreeNode{
        int value;
        TreeNode left;
        TreeNode right;
        public TreeNode(int value){
            this.value = value;
        }
    }
    TreeNode root;
    public BinaryTree(int[] array){
        root = makeBinaryTreeByArray(array,1);
    }

    /**
     * 采用递归的方式创建一颗二叉树
     * 传入的是二叉树的数组表示法
     * 构造后的是二叉树的二叉链表表示法
     * @param array
     * @param index
     * @return
     */
    private static TreeNode makeBinaryTreeByArray(int[] array, int index) {
        if(index<array.length){
            int value = array[index];
            if(value != 0){
                TreeNode t = new TreeNode(value);
                array[index] = 0;
                t.left = makeBinaryTreeByArray(array,index*2);
                t.right = makeBinaryTreeByArray(array,index*2+1);
                return t;
            }
        }
        return null;
    }
    
    /**
     * 深度优先遍历，相当于先根遍历
     * 采用非递归实现
     * 需要辅助的数据结构：栈
     */
    public void depthOrderTraversal(){
        if(root == null){
            System.out.println("empty tree");
            return;
        }
        Stack<TreeNode> stack = new Stack<>();
        stack.push(root);
        while (stack.isEmpty() == false){
            TreeNode node = stack.pop();
            System.out.println("深度遍历结果："+(node.value + " "));
            if(node.right != null){
                stack.push(node.right);

            }
            if(node.left != null){
                stack.push(node.left);

            }

        }
        System.out.println("\n");
    }

    public void levelOrderTraversal(){
        if (root == null){
            System.out.println("empty tree");
            return;
        }

        ArrayDeque<TreeNode> queue=new ArrayDeque<TreeNode>();
        queue.add(root);
        while (queue.isEmpty() == false){
            TreeNode node = queue.remove();
            System.out.println("广度遍历结果："+node.value);
            if(node.left != null){
                queue.add(node.left);
            }
            if(node.right != null){
                queue.add(node.right);
            }
        }
        System.out.println("\n");
    }

    public static void main(String[] args) {
        int[] arr={0,13,65,5,97,25,0,37,22,0,4,28,0,0,32,0};
        BinaryTree tree=new BinaryTree(arr);
        tree.depthOrderTraversal();
        tree.levelOrderTraversal();
    }
}