Time: 92 ms (57.09%), Space: 40.4 MB (80.97%) - LeetHub

Author: JanaSabuj

sum-of-subarray-minimums/sum-of-subarray-minimums.cpp

@@ -0,0 +1,45 @@
+class Solution {
+    const int mod = 1e9 + 7;
+public:
+    int sumSubarrayMins(vector<int>& arr) {
+        int n = arr.size();
+        int area[n][2];
+        
+        // ple
+        stack<int> s;
+        for(int i = 0; i < n; i++){
+            
+            while(!s.empty() and arr[s.top()] > arr[i]) s.pop();
+            if(s.empty())
+                area[i][0] = 0;
+            else
+                area[i][0] = s.top() + 1;
+            s.push(i);
+        }
+                
+        // nle
+        stack<int> st;
+        for(int i = n - 1; i >= 0; i--){            
+            
+            while(!st.empty() and arr[st.top()] >= arr[i]) st.pop();
+            if(st.empty())
+                area[i][1] = n - 1;
+            else
+                area[i][1] = st.top() - 1;
+            st.push(i);
+        }
+        
+        int sum = 0;
+        for(int i = 0; i < n; i++){
+            int lo = area[i][0], hi = area[i][1];
+            // cout << i << " " << lo << " " << hi << endl;
+            long prod = ((i - lo + 1) % mod * (hi - i + 1) % mod) % mod;
+            prod = (prod % mod * arr[i] % mod) % mod;
+            sum = (sum + prod) % mod;
+            // sum = (sum + ((arr[i] % mod * ((i - lo + 1) * (hi - i + 1)) % mod)) % mod) % mod;
+        }
+        
+        cout << mod << endl;
+        return sum ;
+    }
+};