# topic:

And enter the result in a preorder traversal of a binary tree in preorder traversal of the binary tree a rebuild. Suppose Results preorder traversal order and input of duplicate numbers are free. Before entering e.g. preorder traversal sequence {1,2,4,7,3,5,6,8} and {4,7,2,1,5,3,8,6} order traversal sequence, and the reconstructed binary tree return.

# Problem solving:

链接：https://www.nowcoder.com/questionTerminal/8a19cbe657394eeaac2f6ea9b0f6fcf6?answerType=1&f=discussion 来源：牛客网 /** * Definition for binary tree * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ import java.util.Arrays; public class Solution { public TreeNode reConstructBinaryTree(int [] pre,int [] in) { if (pre.length == 0 || in.length == 0) { return null; } The root the TreeNode ; = new new the TreeNode (pre [0 ]); // find the roots in the preamble in order for ( int I = 0; I <in.length; I ++ ) { IF (in [I] == pre [0 ]) { // left subtree, attention copyOfRange functions, left and right to open and close root.left = reConstructBinaryTree (Arrays.copyOfRange (pre,. 1, I +. 1), Arrays.copyOfRange (in, 0 , I)); // right subtree, attention copyOfRange functions, left and right to open and close root.right = reConstructBinaryTree (Arrays.copyOfRange (pre, I +. 1, pre.length), Arrays.copyOfRange (in, I +. 1 , in.length)); BREAK } } return root; } }