二叉树的创建（数组转二叉树） java

将一个数组转换成一个二叉树的java实现，如下：

import org.junit.Test;

import java.util.ArrayList;
import java.util.List;

/**
 * 二叉树的生成
 *
 * @author DangerShi
 */
public class BTreeBuilder {

    class TreeNode {
        Object data;
        TreeNode left;
        TreeNode right;

        public TreeNode() {
        }

        public TreeNode(Object data, TreeNode left, TreeNode right) {
            this.data = data;
            this.left = left;
            this.right = right;
        }
    }

    public TreeNode arrayToBTree(Object[] arrs) {
        if (arrs == null || arrs.length == 0) {
            return new TreeNode();
        }

        List<TreeNode> nodes = new ArrayList<>(arrs.length);
        for (Object obj : arrs) {
            TreeNode treeNode = new TreeNode();
            treeNode.data = obj;
            nodes.add(treeNode);
        }

        for (int i = 0; i < arrs.length/2 - 1; i++) {
            TreeNode node = nodes.get(i);
            node.left = nodes.get(i*2 + 1);
            node.right = nodes.get(i*2 + 2);
        }
        // 只有当总节点数是奇数时，最后一个父节点才有右子节点
        int lastPNodeIndex = arrs.length/2 - 1;
        TreeNode lastPNode = nodes.get(lastPNodeIndex);
        lastPNode.left = nodes.get(lastPNodeIndex*2 + 1);
        if (arrs.length%2 != 0) {
            lastPNode.right = nodes.get(lastPNodeIndex*2 + 2);
        }

        return nodes.get(0);
    }

    @Test
    public void test() {
        /**
         *          1
         *      2       3
         *    4   5   6   7
         */
        TreeNode treeNode = arrayToBTree(new Object[]{1,2,3,4,5,6,7});
    }

}