Create Binary Tree Level Order Traversal.cpp

Author: daizhenyang

Binary Tree Level Order Traversal.cpp

@@ -0,0 +1,47 @@
+/**
+ * Definition for binary tree
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    vector<vector<int> > levelOrder(TreeNode *root) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        if (!root)return vector<vector<int> >();
+        queue<TreeNode *>q;
+        q.push(root);
+        int node_in_now_level=1;
+        int node_in_next_level=0;
+        vector<vector<int> >ans;
+        vector<int>now;
+        while (!q.empty())
+        {
+            TreeNode *p=q.front();
+            q.pop();
+            now.push_back(p->val);
+            node_in_now_level--;
+            if (p->left)
+            {
+                q.push(p->left);
+                node_in_next_level++;
+            }
+            if (p->right)
+            {
+                q.push(p->right);
+                node_in_next_level++;
+            }
+            if (!node_in_now_level)
+            {
+                ans.push_back(now);
+                now.clear();
+                swap(node_in_now_level,node_in_next_level);
+            }
+        }
+        return ans;
+    }
+};