# java-谷歌面试题-给定一个排序数组，如何构造一个二叉排序树

```import java.util.LinkedList;

public class CreateBSTfromSortedArray {

/**
* 题目:给定一个排序数组，如何构造一个二叉排序树
* 递归
*/

public static void main(String[] args) {
int[] data = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
CreateBSTfromSortedArray bst = new CreateBSTfromSortedArray();
Node root = bst.createBST(data);
bst.inOrder(root);
System.out.println();
bst.levelOrder(root);
}

public Node createBST(int[] data) {
if (data == null || data.length == 0) {
return null;
}
Node[] nodes = createNode(data);
return createBSTHelp(nodes, 0, data.length - 1);
}

//Recursion.Node[start...end],find its root.Then find left child and right child for the root.
public Node createBSTHelp(Node[] nodes, int start, int end) {
if (start > end) {
return null;
}
int mid = start + (end - start) / 2;
if (start == end) {
return nodes[mid];
}
Node root = nodes[mid];
root.left = createBSTHelp(nodes, start, mid - 1);
root.right = createBSTHelp(nodes, mid + 1, end);
return root;

}

public Node[] createNode(int[] data) {
int len = data.length;
Node[] nodes = new Node[len];
for (int i = 0; i < len; i++) {
nodes[i] = new Node(data[i]);
}
return nodes;
}

private static class Node {
int data;
Node left;
Node right;

Node(int data) {
this.data = data;
}
}

public void levelOrder(Node node) {
if (node == null)
return;
while (!queue.isEmpty()) {
Node curNode = queue.removeFirst();
System.out.print(curNode.data + " ");
if (curNode.left != null) {
}
if (curNode.right != null) {
}
}
}

public void inOrder(Node node) {
if (node == null) {
return;
}
inOrder(node.left);
System.out.print(node.data + " ");
inOrder(node.right);
}

}

```

java-谷歌面试题-给定一个排序数组，如何构造一个二叉排序树

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