题解 | #输出二叉树的右视图#

public class Solution {
    public int[] solve (int[] xianxu, int[] zhongxu) {
        //将xianxu节点的值映射到相应的中序节点的下标。
        TreeNode root=buildTree(xianxu,zhongxu,0,xianxu.length-1,0,zhongxu.length-1);
        Queue<TreeNode>queue=new LinkedList<>();
        queue.offer(root);
        List<Integer>list=new ArrayList<>();
        while(!queue.isEmpty()){
            int size=queue.size();
            TreeNode cur=null;
            for(int i=0;i<size;i++){
                cur=queue.poll();
                if(cur.left!=null)queue.offer(cur.left);
                if(cur.right!=null)queue.offer(cur.right);
            }
            list.add(cur.val);
        }
        int []r=new int[list.size()];
        for(int i=0;i<list.size();i++)
            r[i]=list.get(i);
        return r;
    }
    
    public TreeNode buildTree(int[]p,int[]v,int pl,int ph,int vl,int vh){
        if(pl>ph)
            return null;
        int vm=vl;
        for(;vm<=vh;vm++)
            if(v[vm]==p[pl])
                break;
        
        TreeNode node=new TreeNode(v[vm]);
        node.left=buildTree(p,v,pl+1,pl+vm-vl,vl,vm-1);
        node.right=buildTree(p,v,pl+vm-vl+1,ph,vm+1,vh);
        return node;
    }
    
}