Adding CSES solution

Author: AK-I-RA

CSES/Maximum Subarray Sum II.cpp

@@ -0,0 +1,70 @@
+#include<bits/stdc++.h>
+#include<iostream>
+#include <sstream>
+using namespace std;
+
+#define mod 1000000007
+#define one(x) __builtin_popcountll(x)
+#define pp pair<ll,ll>
+#define all(x) (x).begin(), (x).end()
+#define removeDuplicates(a) a.resize(unique(all(a))-a.begin())
+typedef long long int ll;
+
+
+
+
+void subMain(){
+    ll n,a,b;cin>>n>>a>>b;
+   	ll ar[n],presum[n];
+   	for(int i=0;i<n;++i)
+   	{
+   		cin>>ar[i];
+	}
+	presum[0]=ar[0];
+	for(int i=1;i<n;++i)
+	{
+		presum[i]=presum[i-1]+ar[i];
+	}
+	multiset<ll>s;
+	s.insert(0);
+	ll ans=-9e18;
+	ans=max(ans,presum[a-1]);
+	int flag=0;
+	for(int i=a;i<n;++i)
+	{
+		if(i-b>=0)
+		{
+			if(!flag)
+			{
+				auto it=s.find(0);
+				s.erase(it);
+				flag=1;
+			}
+		}
+		if(i-a>=0)
+		{
+			s.insert(presum[i-a]);
+		}
+		ans=max(ans,presum[i]-*s.begin());
+		if(i-b>=0)
+		{
+			auto it=s.find(presum[i-b]);
+			s.erase(it);
+		}
+	}
+	cout<<ans<<endl;
+}
+
+int32_t main(){
+
+	ios_base::sync_with_stdio(false);
+	cin.tie(0); cout.tie(0);
+
+
+	/*ll t;
+	cin >> t;
+	while(t--){
+        subMain();
+	}*/
+	subMain();
+}