输入某二叉树的前序遍历和中序遍历的结果，请重建该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。例如，给出
前序遍历 preorder = [3,9,20,15,7] 中序遍历 inorder = [9,3,15,20,7]
返回如下的二叉树：
3
/ 9 20
/ 15 7
限制：
0 <= 节点个数 <= 5000
class Solution {
public TreeNode buildTree(int[] preorder, int[] inorder) {
int n = preorder.length;
if (n == 0)
{
return null;
}
int rootVal = preorder[0], rootIndex = 0;
for (int i = 0; i < n;i++)
{
if (inorder[i] == rootVal)
{
rootIndex = i;
break;
}
}
TreeNode root = new TreeNode(rootVal);
root.left = buildTree(Arrays.copyOfRange(preorder,1,1+rootIndex),Arrays.copyOfRange(inorder,0,rootIndex));
root.right = buildTree(Arrays.copyOfRange(preorder,1+rootIndex,n),Arrays.copyOfRange(inorder,rootIndex + 1, n));
return root;
}
}