leetcode 103. 二叉樹的鋸齒形層次遍歷(Binary Tree Zigzag Level Order Traversal)
阿新 • • 發佈:2019-04-28
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目錄
- 題目描述:
- 示例:
- 解法:
題目描述:
給定一個二叉樹,返回其節點值的鋸齒形層次遍歷。(即先從左往右,再從右往左進行下一層遍歷,以此類推,層與層之間交替進行)。
示例:
給定二叉樹 [3,9,20,null,null,15,7]
,
3
/ 9 20
/ 15 7
返回鋸齒形層次遍歷如下:
[
[3],
[20,9],
[15,7]
]
解法:
/** * Definition for a binary tree node. * struct TreeNode { * int val; * TreeNode *left; * TreeNode *right; * TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */ class Solution { public: vector<vector<int>> zigzagLevelOrder(TreeNode* root) { vector<vector<int>> res; vector<TreeNode*> cur, nxt; bool forward = true; if(root){ cur.push_back(root); vector<int> lst; while(!cur.empty()){ lst.clear(); nxt.clear(); for(TreeNode* node : cur){ lst.push_back(node->val); if(node->left){ nxt.push_back(node->left); } if(node->right){ nxt.push_back(node->right); } } if(forward == false){ forward = true; lst = vector<int>(lst.rbegin(), lst.rend()); }else{ forward = false; } res.push_back(lst); cur = nxt; } } return res; } };
leetcode 103. 二叉樹的鋸齒形層次遍歷(Binary Tree Zigzag Level Order Traversal)