[LeetCode] 103. Binary Tree Zigzag Level Order Traversal

void zzloHelp(vector<vector<int>> &res,unsigned int lev,TreeNode *r){if(!r)return;if(lev+1>res.size()){res.push_back(vector<int>());}res[lev].push_back(r->val);zzloHelp(res,lev+1,r->left);zzloHelp(res,lev+1,r->right);}vector<vector<int>> zigzagLevelOrder(TreeNode* root){vector<vector<int>> res;zzloHelp(res,0,root);for(unsigned int i=0;i<res.size();++i){if(i%2==1){int n=res[i].size();for(int k=0;k<n/2;++k)swap(res[i][k],res[i][n-1-k]);}}return res;}