45 lines
1.5 KiB
C++
45 lines
1.5 KiB
C++
/**
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* Definition for a binary tree node.
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* struct TreeNode {
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* int val;
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* TreeNode *left;
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* TreeNode *right;
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* TreeNode() : val(0), left(nullptr), right(nullptr) {}
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* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
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* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
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* };
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*/
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class Solution {
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public:
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vector<vector<int>> levelOrder(TreeNode* root) {
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vector<vector<int>> result;
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std::queue<TreeNode*> myQueue;
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if(root==nullptr){
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return {};
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}
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// initial setup of the queue
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myQueue.push(root);
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while(!myQueue.empty()){
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int size = myQueue.size();
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vector<int> current_level;
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// assume every node at the next lever is in the queue, visit them one by one.
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for(int i=0;i<size;i++){
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TreeNode* current = myQueue.front();
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myQueue.pop();
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if(current!=nullptr){
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current_level.push_back(current->val);
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// before we get to the next level, push every node of the next level into the queue.
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if(current->left!=nullptr){
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myQueue.push(current->left);
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}
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if(current->right!=nullptr){
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myQueue.push(current->right);
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}
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}
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}
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result.push_back(current_level);
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}
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return result;
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}
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};
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