diff --git a/1120-Maximum-Average-Subtree/cpp-1120/CMakeLists.txt b/1120-Maximum-Average-Subtree/cpp-1120/CMakeLists.txt
new file mode 100644
index 00000000..a9faeff1
--- /dev/null
+++ b/1120-Maximum-Average-Subtree/cpp-1120/CMakeLists.txt
@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.14)
+project(C)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(C main.cpp)
\ No newline at end of file
diff --git a/1120-Maximum-Average-Subtree/cpp-1120/main.cpp b/1120-Maximum-Average-Subtree/cpp-1120/main.cpp
new file mode 100644
index 00000000..b610c81d
--- /dev/null
+++ b/1120-Maximum-Average-Subtree/cpp-1120/main.cpp
@@ -0,0 +1,70 @@
+/// Source : https://leetcode.com/problems/maximum-average-subtree/
+/// Author : liuyubobobo
+/// Time   : 2019-07-13
+
+#include <iostream>
+#include <unordered_map>
+
+using namespace std;
+
+
+/// DFS
+/// Time Complexity: O(n)
+/// Space Complexity: O(n)
+
+/// Definition for a binary tree node.
+struct TreeNode {
+    int val;
+    TreeNode *left;
+    TreeNode *right;
+    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+};
+
+
+class Solution {
+
+private:
+    unordered_map<TreeNode*, int> sum;
+    unordered_map<TreeNode*, int> sz;
+
+public:
+    double maximumAverageSubtree(TreeNode* root) {
+
+        dfsSum(root);
+        dfsSz(root);
+        return dfsRes(root);
+    }
+
+private:
+    int dfsSum(TreeNode* node){
+
+        if(!node) return 0;
+        int left = dfsSum(node->left);
+        int right = dfsSum(node->right);
+        sum[node] = left + right + node->val;
+        return sum[node];
+    }
+
+    int dfsSz(TreeNode* node){
+
+        if(!node) return 0;
+        int left = dfsSz(node->left);
+        int right = dfsSz(node->right);
+        sz[node] = left + right + 1;
+        return sz[node];
+    }
+
+    double dfsRes(TreeNode* node){
+
+        if(!node) return 0;
+        double left = dfsRes(node->left);
+        double right = dfsRes(node->right);
+        return max(max(left, right), (double)sum[node] / sz[node]);
+    }
+};
+
+
+int main() {
+
+    return 0;
+}
\ No newline at end of file
diff --git a/readme.md b/readme.md
index 0fe29c1c..1b62cea3 100644
--- a/readme.md
+++ b/readme.md
@@ -764,4 +764,5 @@ email: [liuyubobobo@gmail.com](mailto:liuyubobobo@gmail.com)
 | | | | | | |
 | 1118 | [Number of Days in a Month](https://leetcode.com/problems/number-of-days-in-a-month/) | [无] | [C++](1118-Number-of-Days-in-a-Month/cpp-1118/) | | |
 | 1119 | [Remove Vowels from a String](https://leetcode.com/problems/remove-vowels-from-a-string/) | [无] | [C++](1119-Remove-Vowels-from-a-String/cpp-1119/) | | |
+| 1120 | [Maximum Average Subtree](https://leetcode.com/problems/maximum-average-subtree/) | [无] | [C++](1120-Maximum-Average-Subtree/cpp-1120/) | | |
 | | | | | | |
\ No newline at end of file