Leetcode/binaryTreeLevelOrderTraversal at main · manahiliqbal/Leetcode · GitHub

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<vector<int>> levelOrder(TreeNode* root) {
        vector<vector<int>> traversal;
        if (root==NULL) return traversal;
        queue <TreeNode*> q;
        q.push(root);
        while (!q.empty()){
            vector <int> level;
            int size = q.size();
            for (int i=0; i<size; i++){
                TreeNode* cur = q.front();
                q.pop();
                level.push_back(cur->val);

                if(cur->left) q.push(cur->left);
                if(cur->right) q.push(cur->right);
            }
            traversal.push_back(level);
        }
        return traversal;
    }
};