199. 二叉树的右视图
199. 二叉树的右视图
题目：
题解：
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<Integer> rightSideView(TreeNode root) {
//用bfs
List<Integer> list = new LinkedList<>();
if(root == null) {
return list;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
while(queue.size()>0) {
int size = queue.size();
for(int i=0;i<size;i++) {
TreeNode node = queue.poll();
if(i==size-1) {
list.add(node.val);
}
if(node.left != null) {
queue.add(node.left);
}
if(node.right != null) {
queue.add(node.right);
}
}
}
return list;
}
}