Create make-k-subarray-sums-equal.cpp

Author: kamyu104

C++/make-k-subarray-sums-equal.cpp

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+// Time:  O(n)
+// Space: O(n)
+
+// math, greedy
+class Solution {
+public:
+    long long makeSubKSumEqual(vector<int>& arr, int k) {
+        const int l = gcd(k, size(arr));
+        int64_t result = 0;
+        for (int i = 0; i < l; ++i) {
+            vector<int> vals;
+            for (int j = i; j < size(arr); j += l) {
+                vals.emplace_back(arr[j]);
+            }
+            nth_element(begin(vals), begin(vals) + size(vals) / 2, end(vals));
+            result += accumulate(cbegin(vals), cend(vals), 0LL,
+                                 [&](const auto& total, const auto& x) {
+                                     return total + abs(x - vals[size(vals) / 2]);
+                                 });
+        }
+        return result;
+    }
+};