LeetCode 199. Binary Tree Right Side View

题目

题意：假如你在一棵二叉树的右边，往左看，能看到哪些元素。

题解：广搜，每一层的最右边元素即可。

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
struct Node
{
    TreeNode* node;
    int num;
    Node(){}
    Node(TreeNode* node,int num)
    {
        this->node = node;
        this->num = num;
    }
};
class Solution {
public:
    vector<int> ans;
    vector<int> rightSideView(TreeNode* root) {
        
        if(root==NULL)
            return ans;
        queue<Node> q;
        q.push(Node(root,0));
        
        int num = 0;
        while(!q.empty())
        {
            Node term = q.front();
            q.pop();
            
            if(q.empty()||q.front().num != term.num)
            {
                ans.push_back(term.node->val);
            }
            
            if(term.node->left!=NULL)
                q.push(Node(term.node->left,term.num+1));
            if(term.node->right!=NULL)
                q.push(Node(term.node->right,term.num+1));
        }
        
        return ans;
        
        
    }
    
};