二叉树的右视图 · 交互式算法学习

这是一组同题正确实现，独立于上方当前动画方法；不同语言可能采用另一种正确策略。

1/**2 * Definition for a binary tree node.3 * public class TreeNode {4 *     int val;5 *     TreeNode left;6 *     TreeNode right;7 *     TreeNode() {}8 *     TreeNode(int val) { this.val = val; }9 *     TreeNode(int val, TreeNode left, TreeNode right) {10 *         this.val = val;11 *         this.left = left;12 *         this.right = right;13 *     }14 * }15 */16class Solution {17    public List<Integer> rightSideView(TreeNode root) {18        List<Integer> ans = new ArrayList<>();19        if (root == null) {20            return ans;21        }22        Deque<TreeNode> q = new ArrayDeque<>();23        q.offer(root);24        while (!q.isEmpty()) {25            ans.add(q.peekFirst().val);26            for (int k = q.size(); k > 0; --k) {27                TreeNode node = q.poll();28                if (node.right != null) {29                    q.offer(node.right);30                }31                if (node.left != null) {32                    q.offer(node.left);33                }34            }35        }36        return ans;37    }38}