Create 29 September Maximum subarray sum 2 (#900)

Author: Chayandas07

29 September Maximum subarray sum 2

@@ -0,0 +1,36 @@
+class Solution {
+  public:
+    int maxSubarrSum(vector<int>& arr, int a, int b) {
+        // code here
+        int n=arr.size();
+        
+        vector<long long> pref(n+1,0);
+        
+        for(int i=1;i<=n;i++){
+            pref[i]=pref[i-1]+arr[i-1];
+        }
+        
+        deque<int> dq;
+        
+        int maxSum=INT_MIN;
+        
+        for(int r=a;r<=n;r++){
+           int l=r-a;
+           
+           while (!dq.empty() && pref[dq.back()] >= pref[l]){
+               dq.pop_back();
+           }
+           
+           dq.push_back(l);
+           
+           while (!dq.empty() && dq.front() < r-b){
+                dq.pop_front();
+           }
+           
+           maxSum=max(maxSum,(int)(pref[r]-pref[dq.front()]));
+        }
+        
+        return maxSum;
+        
+    }
+};