题解 | #输出二叉树的右视图#
输出二叉树的右视图
https://www.nowcoder.com/practice/c9480213597e45f4807880c763ddd5f0
方法：
先用上一道题的建树方法建树，再用层次遍历即可：
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;
}
}
