[leetcode] Binary Tree Right Side View

原创于 2015-06-14 11:41:01 发布 · 303 阅读

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本文介绍了一种方法，通过遍历二叉树并从右侧视角收集节点值，实现从顶部到底部的有序输出。

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From : https://leetcode.com/problems/binary-tree-right-side-view/

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].

/**
 * 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> res;
        if(!root) return res;
        queue<TreeNode> box;
        box.push(*root);
        int up=1, cur=0;
        while(up) {
            TreeNode node(0);
            while(up) {
                up--;
                node = box.front();
				box.pop();
				if(node.left) {box.push(*node.left); cur++;}
                if(node.right) {box.push(*node.right); cur++;}
            }
            res.push_back(node.val);
            up = cur;
            cur = 0;
        }
        return res;
    }
};