牛客-TOP101-BM41

import java.util.*;


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 * 求二叉树的右视图 * @param xianxu int整型一维数组 先序遍历 * @param zhongxu int整型一维数组 中序遍历 * @return int整型一维数组 */
    public TreeNode reConstructBinaryTree(int [] pre,int [] vin) {
    
        int n = pre.length;
        int m = vin.length;
        if(n == 0 || m == 0){
    
            return null;
        }
        TreeNode t = new TreeNode(pre[0]);
        for(int i = 0; i < vin.length; i++){
    
            if(pre[0] == vin[i]){
    
                t.left = reConstructBinaryTree(Arrays.copyOfRange(pre, 1, i+1), Arrays.copyOfRange(vin, 0, i));
                t.right = reConstructBinaryTree(Arrays.copyOfRange(pre, i+1, pre.length), Arrays.copyOfRange(vin, i+1, vin.length));
                break;
            }
        }
        return t;
    }
    
    public ArrayList<Integer> rightSideView(TreeNode root){
    
        ArrayList<Integer> list = new ArrayList<>();
        Deque<TreeNode> deque = new LinkedList<>();
        deque.offerLast(root);
        while(!deque.isEmpty()){
    
            int size = deque.size();
            TreeNode t = null;
            while(size != 0){
    
                t = deque.pollFirst();
                if(t.left != null)
                    deque.offerLast(t.left);
                if(t.right != null)
                    deque.offerLast(t.right);
                size--;
            }
            list.add(t.val);
        }
        return list;
    }
    
    public int[] solve (int[] xianxu, int[] zhongxu) {
    
        // write code here
        if(xianxu.length == 0 || zhongxu.length == 0){
    
            return new int[0];
        }
        TreeNode root = reConstructBinaryTree(xianxu, zhongxu);
        
        ArrayList<Integer> list = rightSideView(root);

        int[] res = new int[list.size()];
        for(int i = 0; i < list.size(); i++)
            res[i] = list.get(i);
        return res;
    }
}