Binary Tree Right Side View

好久没有刷leetcode了，要继续了。。

今天第一题。

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].

一看到就觉得是层次遍历，而且每层的最后一个结点会保存下来。

C++实现代码：

#include<iostream> #include<new> #include<vector> #include<queue>

using namespace std; //Definition for binary tree

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) { if(root==NULL) return vector<int>(); vector<int> res; queue<TreeNode*> q; q.push(root); int cur=1; while(!q.empty()) { int rcur=0; while(cur) { TreeNode *tmp=q.front(); q.pop(); cur--; if(cur==0) res.push_back(tmp->val); if(tmp->left) { q.push(tmp->left); rcur++; } if(tmp->right) { q.push(tmp->right); rcur++; } } cur=rcur; } return res; } void createTree(TreeNode *&root) { int i; cin>>i; if(i!=0) { root=new TreeNode(i); if(root==NULL) return; createTree(root->left); createTree(root->right); } } }; int main() { Solution s; TreeNode *root; s.createTree(root); vector<int> vec; vec=s.rightSideView(root); for(auto a:vec) cout<<a<<" "; cout<<endl; }