【LeetCode】Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder traversal of a tree, construct the binary tree.

Note:
You may assume that duplicates do not exist in the tree.

public class Solution {
    public TreeNode buildTree(int[] preorder, int[] inorder) {
        if(preorder.length==0||inorder.length==0)
            return null;
        return BuildTreeNode(preorder,0,preorder.length-1,inorder,0,inorder.length-1);

    }

    private TreeNode BuildTreeNode(int[] preorder, int prestart, int preend, int[] inorder,
            int instart, int inend) {
        if(prestart>preend||instart>inend)
            return null;
        int temp = preorder[prestart];
        TreeNode root = new TreeNode(temp);
        int leftlength=0;

        for(int i=instart;i<=inend;i++){
            if(inorder[i]!=temp)
                leftlength++;
            else if(inorder[i]==temp)
                break;
        }
        root.left=BuildTreeNode(preorder, prestart+1, prestart+leftlength, inorder, instart,instart+leftlength-1);
        root.right=BuildTreeNode(preorder,prestart+leftlength+1,preend,inorder,instart+leftlength+1,inend);
        return root;
    }
}