Create 2355.Maximum-Number-of-Books-You-Can-Take.cpp

Stack/2355.Maximum-Number-of-Books-You-Can-Take/2355.Maximum-Number-of-Books-You-Can-Take.cpp

@@ -0,0 +1,33 @@
+using LL = long long;
+class Solution {
+public:
+    long long maximumBooks(vector<int>& books) 
+    {
+        int n = books.size();
+        vector<LL>dp(n);
+        stack<LL>stk;
+
+        LL ret = 0;
+        for (int i=0; i<n; i++)
+        {
+            while (!stk.empty() && books[stk.top()] > books[i]-(i-stk.top()))            
+                stk.pop();
+
+            if (!stk.empty())
+            {
+                LL d = i - stk.top();
+                dp[i] = dp[stk.top()] + ((LL)books[i] + (LL)books[i] - d + 1) * d /2;                
+            }
+            else
+            {
+                LL d = min(i + 1, books[i]);
+                dp[i] = ((LL)books[i] + (LL)books[i] - d + 1) * d /2;                
+            }
+            stk.push(i);
+
+            ret = max(ret, dp[i]);
+        }
+
+        return ret;        
+    }
+};