非递归构建

public class BinaryTree {

    public TreeNode root;

    public BinaryTree(int[] array) {
        root = createBinaryTree(array, 0);
    }

    /**
     * 创建二叉树
     *
     * @param array
     * @param index
     * @return
     */
    private TreeNode createBinaryTree(int[] array, int index) {
        TreeNode treeNode = null;
        if (index < array.length) {
            treeNode = new TreeNode(array[index]);
            // 对于顺序存储的完全二叉树，如果某个节点的索引为index，
            // 其对应的左子树的索引为2 * index + 1，右子树为 2 * index + 2
            treeNode.left = createBinaryTree(array, 2 * index + 1);
            treeNode.right = createBinaryTree(array, 2 * index + 2);
        }
        return treeNode;
    }
}

class TreeNode {
    public int data;
    public TreeNode left;
    public TreeNode right;

    public TreeNode(int data) {
        super();
        this.data = data;
    }

    @Override
    public String toString() {
        return data + " ";
    }
}