Create constrained-subset-sum.cpp

Author: kamyu104

C++/constrained-subset-sum.cpp

@@ -0,0 +1,24 @@
+// Time:  O(n)
+// Space: O(k)
+
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        int result = numeric_limits<int>::min();
+        deque<pair<int, int>> dq;
+        for (int i = 0; i < nums.size(); ++i) {
+            if (!dq.empty() && i - dq.front().first == k + 1) {
+                dq.pop_front();
+            }
+            const auto& curr = nums[i] + (!dq.empty() ? dq.front().second : 0);
+            while (!dq.empty() && dq.back().second < curr) {
+                dq.pop_back();
+            }
+            if (curr > 0) {
+                dq.emplace_back(i, curr);
+            }
+            result = max(result, curr);
+        }
+        return result;
+    }
+};