Binary Tree Right Side View
出处
Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.
For example:
Given the following binary tree,
1 <---
/ \
2 3 <---
\ \
5 4 <---
You should return [1, 3, 4].
Solution
每一层只取最后加入数组的那一个元素
Complexity
时间复杂度 O(n),空间复杂度 O(n)
Code
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public List<Integer> rightSideView(TreeNode root) {
List<Integer> result = new ArrayList<Integer>();
List<TreeNode> curr = new ArrayList<TreeNode>();
if (root == null) {
return result;
}
curr.add(root);
while (curr.isEmpty() == false) {
List<TreeNode> next = new ArrayList<TreeNode>();
for (int i = 0; i < curr.size(); i++) {
if (i == curr.size() - 1) {
result.add(curr.get(i).val);
}
if (curr.get(i).left != null) {
next.add(curr.get(i).left);
}
if (curr.get(i).right != null) {
next.add(curr.get(i).right);
}
}
curr.clear();
curr = next;
}
return result;
}
}