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
        if (preOrder.length == 0 || vinOrder.length == 0)return null;
        TreeNode root = new TreeNode(preOrder[0]);
        for (int i = 0; i < vinOrder.length; i++) {
            if (vinOrder[i] == preOrder[0]) {
                int[] leftPre = new int[i];
                System.arraycopy(preOrder, 1, leftPre, 0, i);
                int[] rightPre = new int[preOrder.length - i - 1];
                System.arraycopy(preOrder, 1 + i, rightPre, 0, rightPre.length);
                int[] leftVin = new int[i];
                System.arraycopy(vinOrder, 0, leftVin, 0, i);
                int[] rightVin = new int[vinOrder.length - i - 1];
                System.arraycopy(vinOrder, 1 + i, rightVin, 0, rightVin.length);
                root.left = reConstructBinaryTree(leftPre, leftVin);
                root.right = reConstructBinaryTree(rightPre, rightVin);
                break;
            }
        }
        return root;
    }
}

使用递归，分别构建左右子树