Problem Difficulty Level: Hard

Author: Naganathan05

Monotonic Queue/1425. Constrained Subsequence Sum.cpp

@@ -0,0 +1,34 @@
+/*-------------------------
+  Time Complexity: O(n)
+  Space Complexity: O(n)
+---------------------------*/
+
+class Solution {
+public:
+    int constrainedSubsetSum(vector<int>& nums, int k) {
+        
+        int n = nums.size();
+        int maxSum = nums[0];
+        deque<pair<int,int>> dp;
+        dp.push_back({0, nums[0]});
+
+        for(int i = 1; i < n; i++)
+        {
+            if(i - dp.front().first > k) dp.pop_front();
+            
+            int current = nums[i];
+            if(dp.front().second > 0) current += dp.front().second;
+            maxSum = max(current, maxSum);
+
+            while(!dp.empty() && dp.back().second < current) dp.pop_back();
+            dp.push_back({i, current});
+        }
+
+        return maxSum;
+    }
+};
+
+/*
+Question Link: https://leetcode.com/problems/constrained-subsequence-sum/
+Author: M.R.Naganathan
+*/