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) {
        return constructBinaryTree(preOrder,0,preOrder.length-1,vinOrder,0,vinOrder.length);
    }
    private TreeNode constructBinaryTree(int[] preOrder,int preStart,int preEnd,int[] vinOrder,int vinStart,int vinEnd){
        if(preStart > preEnd) return null;
        int index = 0;
        for(int i=vinStart;i<=vinEnd;i++){
            if(preOrder[preStart] == vinOrder[i]){
                index = i;
                break;
            }
        }
        int leftSize = index - vinStart;
        TreeNode root = new TreeNode(preOrder[preStart]);
        root.left = constructBinaryTree(preOrder,preStart+1,preStart+leftSize,vinOrder,vinStart,index-1);
        root.right = constructBinaryTree(preOrder,preStart+leftSize+1,preEnd,vinOrder,index+1,vinEnd);
        return root;
    }
}