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面试题 04.03. 特定深度节点链表

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Symbols count in article: 913 Reading time ≈ 1 mins.

面试题 04.03. 特定深度节点链表

level-order traversal

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    vector<ListNode*> listOfDepth(TreeNode* tree) {
        if(!tree)
            return {};
        queue<TreeNode*> q;
        vector<ListNode*> ret;
        q.push(tree);
        while(!q.empty())
        {
            ListNode tmp; 
            ListNode* pseudoHead = &tmp;
            for(int i = 0, j = q.size(); i < j; ++i)
            {
                auto p = q.front();
                q.pop();
                pseudoHead->next = new ListNode(p->val);
                pseudoHead = pseudoHead->next;
                if(p->left)
                    q.push(p->left);
                if(p->right)
                    q.push(p->right);
            }
            ret.push_back(tmp.next);
        }
        return ret;
    }
};