Create sum-of-subarray-ranges.cpp

Author: kamyu104

C++/sum-of-subarray-ranges.cpp

@@ -0,0 +1,30 @@
+// Time:  O(n)
+// Space: O(n)
+
+class Solution {
+public:
+    long long subArrayRanges(vector<int>& nums) {
+        int64_t result = 0;
+        vector<int> stk;
+        for (int i = 0; i <= size(nums); ++i) {
+            const int x = (i < size(nums)) ? nums[i] : numeric_limits<int>::max();
+            while (!empty(stk) && nums[stk.back()] <= x) {
+                const int64_t j = stk.back(); stk.pop_back();
+                const int64_t k = !empty(stk) ? stk.back() : -1;
+                result += nums[j] * (j - k) * (i - j);
+            }
+            stk.emplace_back(i);
+        }
+        stk.clear();
+        for (int i = 0; i <= size(nums); ++i) {
+            const int x = (i < size(nums)) ? nums[i] : numeric_limits<int>::min();
+            while (!empty(stk) && nums[stk.back()] >= x) {
+                const int64_t j = stk.back(); stk.pop_back();
+                const int64_t k = !empty(stk) ? stk.back() : -1;
+                result -= nums[j] * (j - k) * (i - j);
+            }
+            stk.emplace_back(i);
+        }
+        return result;
+    }
+};