题解 | #重建二叉树#

import java.util.*;
/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public TreeNode reConstructBinaryTree(int [] pre,int [] vin) {
        int m = pre.length;
        int n = vin.length;
        if(m == 0){
            return null;
        }
        TreeNode root = new TreeNode(pre[0]);
        for(int i = 0; i < vin.length; i++){
            if(vin[i] == pre[0]){
                //找到根节点,将中序遍历分为左右部分
                //左孩子是pre[1]到pre[i],右孩子结点是pre[i+1]到pre[m-1]
                //vin的范围是,左孩子是vin[0]到vin[i-1]
                //右孩子是vin[i+1]到vin[n-1]
                root.left = reConstructBinaryTree(Arrays.copyOfRange(pre,1,i+1),Arrays.copyOfRange(vin,0,i));
                root.right = reConstructBinaryTree(Arrays.copyOfRange(pre,i+1,m),Arrays.copyOfRange(vin,i+1,n));

            }
        }
        return root;
    }
}