diff --git a/cpp/239-Sliding-Window-Maximum.cpp b/cpp/239-Sliding-Window-Maximum.cpp
new file mode 100644
index 000000000..b374dd748
--- /dev/null
+++ b/cpp/239-Sliding-Window-Maximum.cpp
@@ -0,0 +1,25 @@
+class Solution {
+public:
+    vector<int> maxSlidingWindow(vector<int>& nums, int k) {
+        vector<int> res;
+        // monotonically decreasing queue. saves index
+        deque<int> q;
+        for (int l = 0, r = 0; r < nums.size(); ++r) {
+            // only need to keep biggest value from the window, so pop elements smaller than new element from q
+            while (!q.empty() && nums[q.back()] < nums[r]) {
+                q.pop_back();
+            }
+            q.push_back(r);
+            
+            // remove passed elements from window
+            if (l > q.front())
+                q.pop_front();
+
+            if ((r + 1) >= k) {
+                res.push_back(nums[q.front()]);
+                ++l;
+            }
+        }
+        return res;
+    }
+};