请问有没有人会解答,帮助我一下,我不会,帮我答一下吧,如果有会的
class Solution {
public:
vector<vector<int> > Print(TreeNode* pRoot) {
vector<vector<int>> ans;
if(!pRoot) return ans;
stack<TreeNode*> stack1;
stack<TreeNode*> stack2;
stack1.push(pRoot);
while(!stack1.empty() || !stack2.empty()){
vector<int> tmp_ans1;
while(!stack1.empty()){//出栈顺序是从左到右时,将子节点也按从左到右的顺序压入stack2,这样stack2的出栈顺序就是从右往左
TreeNode* tmp = stack1.top();
stack1.pop();
tmp_ans1.push_back(tmp->val);
if(tmp->left){
stack2.push(tmp->left);
}
if(tmp->right){
stack2.push(tmp->right);
}
}
if(!tmp_ans1.empty()) ans.push_back(tmp_ans1);
tmp_ans1.clear();
while(!stack2.empty()){//出栈顺序是从右到左时,将子节点也按照从右到左的顺序压住stack1,这样stack1的出栈顺序就是从左往右
TreeNode* tmp = stack2.top();
stack2.pop();
tmp_ans1.push_back(tmp->val);
if(tmp->right) stack1.push(tmp->right);
if(tmp->left) stack1.push(tmp->left);
}
if(!tmp_ans1.empty()) ans.push_back(tmp_ans1);
}
return ans;
}
};