Binary Tree Right Side View

标签：binary tree right si   leetcode   

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].

Credits:
Special thanks to @amrsaqr for adding this problem and creating all test cases.

/**
 * 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) {
        vector<int> r;
        if(!root){
            return r;
        }
        queue<TreeNode*> q;
        q.push(root);
        q.push(NULL);//用NULL分开层与层
        TreeNode *prev;
        do{
            TreeNode *n=q.front();
            q.pop();
            if(n){
                prev=n;
                if(n->left){
                    q.push(n->left);
                }
                if(n->right){
                    q.push(n->right);
                }
            }else{
                r.push_back(prev->val);//NULL前一个元素就是每层的最右边的元素
                if(!q.empty()){
                    q.push(NULL);
                }
            }
        }while(!q.empty());
        return r;
    }
};

Binary Tree Right Side View

标签：binary tree right si   leetcode   

原文地址：http://blog.csdn.net/u010786672/article/details/44870791