题解 | #重建二叉树#

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param preOrder int整型一维数组
     * @param vinOrder int整型一维数组
     * @return TreeNode类
     */
    public TreeNode reConstructBinaryTree (int[] preOrder, int[] vinOrder) {
        // write code here递归二叉树
        int a = preOrder.length;//前序
        int b = vinOrder.length;//中序
        //数组不可为null
        if (a == 0 || b == 0) {
            return null;
        }
        //根节点
        TreeNode treeNode = new TreeNode(preOrder[0]);
        for (int i = 0; i < b; i++) {
            if (preOrder[0] == vinOrder[i]) {
                //左树
                treeNode.left = reConstructBinaryTree(Arrays.copyOfRange
                    (preOrder, 1, i + 1), Arrays.copyOfRange(vinOrder, 0, i ));
                //右树
                treeNode.right = reConstructBinaryTree(Arrays.copyOfRange
                    (preOrder, i + 1, a), Arrays.copyOfRange(vinOrder, i + 1, b));
                break;
            }
        }
        return  treeNode;
    }
}