【关关的刷题日记61】Leetcode 102. Binary Tree Level Order Traversal- 专知

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【关关的刷题日记61】Leetcode 102. Binary Tree Level Order Traversal

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关关的刷题日记61 – Leetcode 102. Binary Tree Level Order Traversal

题目

题目的意思是让我们按照二叉树每一层的顺序来从根节点到叶子节点、从左到右遍历二叉树。

思路

思路：采用宽度优先搜索，从上到下，从左到右遍历二叉树。

class Solution {public:
    vector<vector<int>> levelOrderBottom(TreeNode* root) {
        vector<vector<int> >store;
        if(root==nullptr)
            return store;
        vector<TreeNode*>bfs;
        bfs.push_back(root);      
        int n=1, count=0;
        while(!bfs.empty())
        {
            vector<int>re;
            for(int i=0; i<n; i++)
            {
                TreeNode *temp=bfs[0];
                bfs.erase(bfs.begin());
                re.push_back(temp->val);
                if(temp->left)
                {
                    bfs.push_back(temp->left);
                    count++;    
                }
                if(temp->right)
                {
                    bfs.push_back(temp->right);
                    count++;
                }
            }
                store.push_back(re);
                n=count;
                count=0;    
        }
        return store;
    }};