题目描述
请实现一个函数按照之字形打印二叉树，即第一行按照从左到右的顺序打印，第二层按照从右至左的顺序打印，第三行按照从左到右的顺序打印，其他行以此类推。
1 /* 2 struct TreeNode { 3 int val; 4 struct TreeNode *left; 5 struct TreeNode *right; 6 TreeNode(int x) : 7 val(x), left(NULL), right(NULL) { 8 } 9 }; 10 */ 11 12 class Solution { 13 public: 14 vector<vector<int>> v; 15 vector<int> vc; 16 stack<TreeNode*> s1; 17 stack<TreeNode*> s2; 18 queue<TreeNode*> q; 19 20 vector<vector<int>> Print(TreeNode* pRoot) { 21 if (!pRoot) 22 return v; 23 q.push(pRoot); 24 while (!s1.empty() || !q.empty()){ 25 while (!q.empty()){ 26 vc.push_back(q.front()->val); 27 if (q.front()->left != NULL) 28 s1.push(q.front()->left); 29 if (q.front()->right != NULL) 30 s1.push(q.front()->right); 31 q.pop(); 32 } 33 if (!vc.empty()){ 34 v.push_back(vc); 35 vc.clear(); 36 } 37 38 while (!s1.empty()){ 39 vc.push_back(s1.top()->val); 40 s2.push(s1.top()); 41 s1.pop(); 42 } 43 while (!s2.empty()){ 44 if (s2.top()->left != NULL) 45 q.push(s2.top()->left); 46 if (s2.top()->right != NULL) 47 q.push(s2.top()->right); 48 s2.pop(); 49 } 50 if (!vc.empty()){ 51 v.push_back(vc); 52 vc.clear(); 53 } 54 } 55 return v; 56 } 57 58 };