Create sum-of-special-evenly-spaced-elements-in-array.cpp

Author: kamyu104

C++/sum-of-special-evenly-spaced-elements-in-array.cpp

@@ -0,0 +1,32 @@
+// Time:  O(n * sqrt(n))
+// Space: O(n * sqrt(n))
+
+class Solution {
+public:
+    vector<int> solve(vector<int>& nums, vector<vector<int>>& queries) {
+        static const int MOD = 1e9 + 7;
+        
+        vector<vector<vector<int>>> prefix(floor(sqrt(size(queries))) + 1, vector<vector<int>>(floor(sqrt(size(queries))) + 1));
+        vector<int> result;
+        for (const auto& query : queries) {
+            int x = query[0], y = query[1];
+            if (uint64_t(y) * y > size(queries)) {
+                int total = 0;
+                for (int i = x; i < size(nums); i += y) {
+                    total = (total + nums[i]) % MOD;
+                }
+                result.emplace_back(total);
+            } else {
+                int begin = x % y;
+                if (empty(prefix[begin][y])) {
+                    prefix[begin][y].emplace_back(0);
+                    for (int i = begin; i < size(nums); i += y) {
+                        prefix[begin][y].emplace_back((prefix[begin][y].back() + nums[i]) % MOD);
+                    }
+                }
+                result.emplace_back((prefix[begin][y].back() - prefix[begin][y][x / y] + MOD) % MOD);
+            }
+        }
+        return result;
+    }
+};