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p199

admin 11月 12, 2020 0

LeetCode p199 Binary Tree Right Side View 题解

1.题目：

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].

题意：

给你一个二叉树，返回它从右边看过去是一个什么样的列表。【从上往下排列】

2.解题思路:

见代码
搜索最右。

3.代码

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 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class  {
    public List<Integer> rightSideView(TreeNode root) {
    List<Integer> ans = new ArrayList<Integer>();
		helper(root, 0, ans);
		return ans;
	}

	public void helper(TreeNode root, int j, List<Integer> ans) {

	if (root == null)
			return;
		if (ans.size() <= j)
			ans.add(root.val);
		helper(root.right, j + 1, ans);
		helper(root.left, j + 1, ans);
	}
}

4.一些总结：