Create 102. Binary Tree Level Order Traversal.md

solutions/102. Binary Tree Level Order Traversal.md

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+# [102. Binary Tree Level Order Traversal](https://leetcode.com/problems/binary-tree-level-order-traversal/)
+# 思路
+层序遍历二叉树。已经在[107题题解](https://github.com/ShusenTang/LeetCode/blob/master/solutions/107.%20Binary%20Tree%20Level%20Order%20Traversal%20II.md)分析过了。
+
+时空复杂度均O(n)
+
+# C++
+``` C++
+class Solution {
+public:
+    vector<vector<int>> levelOrder(TreeNode* root) {
+        vector<vector<int>>res;
+        if(root == NULL) return res;
+        queue<TreeNode *>q;
+        TreeNode *p;
+        
+        q.push(root);
+        while(!q.empty()){
+            vector<int>level;
+            for(int i = q.size(); i > 0; i--){
+                p = q.front();
+                q.pop();
+                level.push_back(p -> val);
+                if(p -> left) q.push(p -> left);
+                if(p -> right) q.push(p -> right);
+            }
+            res.push_back(level);
+        }
+        return res;
+    }
+};
+```