lintcode_69_二叉樹的層次遍歷

二叉樹的層次遍歷

• 描述
• 筆記
• 數據
• 評測

給出一棵二叉樹，返回其節點值的層次遍歷（逐層從左往右訪問）

給一棵二叉樹 {3,9,20,#,#,15,7} ：

  3
 / \
9  20
  /  \
 15   7

返回他的分層遍歷結果：

[
  [3],
  [9,20],
  [15,7]
]

/**
 * Definition of TreeNode:
 * class TreeNode {
 * public:
 *     int val;
 *     TreeNode *left, *right;
 *     TreeNode(int val) {
 *         this->val = val;
 *         this->left = this->right = NULL;
 *     }
 * }
 */


class Solution {
public:
    /*
     * @param root: A Tree
     * @return: Level order a list of lists of integer
     */
    vector<vector<int>> levelOrder(TreeNode * root) {
        // write your code here
        queue<TreeNode*> q;
        vector<vector<int>> ans;
        if(root==NULL)
            return ans;
        int len;
        q.push(root);
        while(!q.empty())
        {
            len=q.size();
            vector<int> res;
            while(len--)
            {
               TreeNode *p=q.front();
               q.pop();
               res.push_back(p->val);
               if(p->left)
                    q.push(p->left);
                if(p->right)
                    q.push(p->right);
                
            }
            ans.push_back(res);
        }
        return ans;
    }
};