LeetCode (Binary Tree Right Side View)

胡为乎遑遑于何之

于 2017-08-16 18:37:35 发布

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分类专栏： C++

本文链接：https://blog.youkuaiyun.com/m0_37705274/article/details/77263319

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本文介绍了一种算法，该算法可以解决给定二叉树的问题，即站在二叉树右侧从上到下看到的节点值。通过递归地遍历左右子树并收集顶部可见节点值来实现。

Problem:

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:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> rightSideView(TreeNode* root) {
        vector<int> ans;
        if(!root) return ans;
        vector<int> right = rightSideView(root->right);
        vector<int> left = rightSideView(root->left);
        ans.push_back(root->val);
        for(auto n : right)
            ans.push_back(n);
        for(int i = right.size(); i < left.size(); i++)
            ans.push_back(left[i]);
        return ans;
    }
};