重建二叉树

Posted 2021-02-17 tu9oh0st

题目描述

输入某二叉树的前序遍历和中序遍历的结果，请重建出该二叉树。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。例如输入前序遍历序列{1,2,4,7,3,5,6,8}和中序遍历序列{4,7,2,1,5,3,8,6}，则重建二叉树并返回。

分析

贴出代码

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
import java.util.*;
public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] in) {
        if (pre.length == 0 || in.length == 0){
             return null;
         }
         TreeNode node = new TreeNode(pre[0]);
         for (int i = 0; i < in.length ; i++){
             if (pre[0] == in[i]){
                 node.left = reConstructBinaryTree(Arrays.copyOfRange(pre,1,i+1),Arrays.copyOfRange(in,0,i));
                 node.right = reConstructBinaryTree(Arrays.copyOfRange(pre,i + 1,pre.length),Arrays.copyOfRange(in, i + 1,in.length));
             }
         }
         return node;
    }
}