diff --git a/1124-Longest-Well-Performing-Interval/cpp-1124/CMakeLists.txt b/1124-Longest-Well-Performing-Interval/cpp-1124/CMakeLists.txt
new file mode 100644
index 00000000..fd2e1e0c
--- /dev/null
+++ b/1124-Longest-Well-Performing-Interval/cpp-1124/CMakeLists.txt
@@ -0,0 +1,6 @@
+cmake_minimum_required(VERSION 3.14)
+project(C)
+
+set(CMAKE_CXX_STANDARD 14)
+
+add_executable(C main3.cpp)
\ No newline at end of file
diff --git a/1124-Longest-Well-Performing-Interval/cpp-1124/main.cpp b/1124-Longest-Well-Performing-Interval/cpp-1124/main.cpp
new file mode 100644
index 00000000..52c10eea
--- /dev/null
+++ b/1124-Longest-Well-Performing-Interval/cpp-1124/main.cpp
@@ -0,0 +1,39 @@
+/// Source : https://leetcode.com/problems/longest-well-performing-interval/
+/// Author : liuyubobobo
+/// Time   : 2019-07-13
+
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+
+/// Presum + Brute Force
+/// Time Complexity: O(n^2)
+/// Space Complexity: O(n)
+class Solution {
+public:
+    int longestWPI(vector<int>& hours) {
+
+        for(int& e: hours)
+            e = (e > 8 ? 1 : 0);
+
+        int n = hours.size();
+        vector<int> presum(n + 1, 0);
+        for(int i = 1; i <= n; i ++)
+            presum[i] = presum[i - 1] + hours[i - 1];
+
+        int best = 0;
+        for(int end = 0; end < n; end ++)
+            for(int start = 0; start <= end && end - start + 1 > best; start ++)
+                if((presum[end + 1] - presum[start]) * 2 > end - start + 1)
+                    best = max(best, end - start + 1);
+        return best;
+    }
+};
+
+
+int main() {
+
+    return 0;
+}
\ No newline at end of file
diff --git a/1124-Longest-Well-Performing-Interval/cpp-1124/main2.cpp b/1124-Longest-Well-Performing-Interval/cpp-1124/main2.cpp
new file mode 100644
index 00000000..275fba3d
--- /dev/null
+++ b/1124-Longest-Well-Performing-Interval/cpp-1124/main2.cpp
@@ -0,0 +1,57 @@
+/// Source : https://leetcode.com/problems/longest-well-performing-interval/
+/// Author : liuyubobobo
+/// Time   : 2019-07-15
+
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+
+/// Presum + Binary Search
+/// Time Complexity: O(n)
+/// Space Complexity: O(n)
+class Solution {
+public:
+    int longestWPI(vector<int>& hours) {
+
+        for(int& e: hours)
+            e = (e > 8 ? 1 : -1);
+
+        int n = hours.size();
+        vector<int> presum(n + 1, 0);
+        for(int i = 1; i <= n; i ++)
+            presum[i] = presum[i - 1] + hours[i - 1];
+
+        int l = 0, r = n;
+        while(l < r){
+            int mid = (l + r + 1) / 2;
+            if(ok(presum, mid))
+                l = mid;
+            else
+                r = mid - 1;
+        }
+        return l;
+    }
+
+private:
+    bool ok(const vector<int>& presum, int len){
+
+        int minv = INT_MAX;
+        for(int i = 0; i + len < presum.size(); i ++){
+            minv = min(minv, presum[i]);
+            if(presum[i + len] - minv > 0)
+                return true;
+        }
+        return false;
+    }
+};
+
+
+int main() {
+
+    vector<int> hours = {9,9,6,0,6,6,9};
+    cout << Solution().longestWPI(hours) << endl;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/1124-Longest-Well-Performing-Interval/cpp-1124/main3.cpp b/1124-Longest-Well-Performing-Interval/cpp-1124/main3.cpp
new file mode 100644
index 00000000..78331388
--- /dev/null
+++ b/1124-Longest-Well-Performing-Interval/cpp-1124/main3.cpp
@@ -0,0 +1,46 @@
+/// Source : https://leetcode.com/problems/longest-well-performing-interval/
+/// Author : liuyubobobo
+/// Time   : 2019-07-15
+
+#include <iostream>
+#include <vector>
+#include <unordered_map>
+
+using namespace std;
+
+
+/// Presum + Hash Map
+/// Time Complexity: O(n)
+/// Space Complexity: O(n)
+class Solution {
+public:
+    int longestWPI(vector<int>& hours) {
+
+        for(int& e: hours)
+            e = (e > 8 ? 1 : -1);
+
+        int n = hours.size();
+        vector<int> presum(n + 1, 0);
+        for(int i = 1; i <= n; i ++)
+            presum[i] = presum[i - 1] + hours[i - 1];
+
+        unordered_map<int, int> pos;
+        int res = 0;
+        for(int i = 1; i <= n; i ++)
+            if(presum[i] > 0) res = max(res, i);
+            else{
+                if(!pos.count(presum[i])) pos[presum[i]] = i;
+                if(pos.count(presum[i] - 1)) res = max(res, i - pos[presum[i] - 1]);
+            }
+        return res;
+    }
+};
+
+
+int main() {
+
+    vector<int> hours = {9,9,6,0,6,6,9};
+    cout << Solution().longestWPI(hours) << endl;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/readme.md b/readme.md
index b9fecfb4..b069504c 100644
--- a/readme.md
+++ b/readme.md
@@ -766,4 +766,6 @@ email: [liuyubobobo@gmail.com](mailto:liuyubobobo@gmail.com)
 | 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/) | | |
 | 1121 | [Divide Array Into Increasing Sequences](https://leetcode.com/problems/divide-array-into-increasing-sequences/) | [无] | [C++](1121-Divide-Array-Into-Increasing-Sequences/cpp-1121/) | | |
+| | | | | | |
+| 1124 | [Longest Well-Performing Interval](https://leetcode.com/problems/longest-well-performing-interval/) | [无] | [C++](1124-Longest-Well-Performing-Interval/cpp-1124/) | | |
 | | | | | | |
\ No newline at end of file