leetcode/102.binary-tree-level-order-traversal.cpp at master · wsycqyz/leetcode · GitHub

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/*
 * @lc app=leetcode id=102 lang=cpp
 *
 * [102] Binary Tree Level Order Traversal
 */

// @lc code=start
/**
 * 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> >  result;
        if (!root) return result;
        queue<TreeNode*> q;
        q.push(root);
        q.push(NULL);
        vector<int> cur_vec;
        while(!q.empty()) {
            TreeNode* t = q.front();
            q.pop();
            if (t==NULL) {
                result.push_back(cur_vec);
                cur_vec.resize(0);
                if (q.size() > 0) {
                    q.push(NULL);
                }
            } else {
                cur_vec.push_back(t->val);
                if (t->left) q.push(t->left);
                if (t->right) q.push(t->right);
            }
        }
        return result;
    }
};
// @lc code=end