题解 | 剑指offer | #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]);
        int index = 0;
        for(int i = 0; i < preOrder.length; i ++){
            if(preOrder[0] == vinOrder[i]) index = i;
        }
        
        int[] pre_left = Arrays.copyOfRange(preOrder, 1, index + 1);
        int[] vin_left = Arrays.copyOfRange(vinOrder, 0, index);
        root.left = reConstructBinaryTree(pre_left, vin_left);

        int[] pre_right = Arrays.copyOfRange(preOrder, index + 1, preOrder.length);
        int[] vin_right = Arrays.copyOfRange(vinOrder, index + 1, vinOrder.length);
        root.right = reConstructBinaryTree(pre_right, vin_right);
	  
        return root;
    }

}