leetcode

commit bedd45bbdb069ba6bcc4df16577bd6fd2e2c1a1d
parent ab95956f801403524c6fd1f7d6a904f5b26cadeb
Author: Jack Sangdahl <jack@pngu.org>
Date:   Thu, 30 Apr 2026 18:51:01 -0600

396. rotate function

Diffstat:
A
rotate_function.c
 | 
35
+++++++++++++++++++++++++++++++++++
A
rotate_function.py
 | 
29
+++++++++++++++++++++++++++++

2 files changed, 64 insertions(+), 0 deletions(-)
diff --git a/rotate_function.c b/rotate_function.c
@@ -0,0 +1,35 @@
+// 396. Rotate Function
+#include "leetcode.h"
+
+/*
+ * you are given an integer array 'nums' of length 'n'. assume 'arr_k' to be an
+ * array obtained by rotating 'nums' by 'k' positions clockwise. we define the
+ * rotation function 'F' on 'nums' as follows: 'F(k) = 0 * arr_k[0] + 1 *
+ * arr_k[1] + ... + (n - 1) * arr_k[n - 1]'. return the maximum value of 'F(0),
+ * F(1), ..., F(n - 1)'. the test cases are generated such that the answer fits
+ * in a 32-bit integer.
+ */
+
+int maxRotateFunction(int *nums, int numsSize) {
+  int f = 0, sum = 0;
+  for (int i = 0; i < numsSize; i++) {
+    f += i * nums[i];
+    sum += nums[i];
+  }
+  int ans = f;
+  for (int i = numsSize - 1; i > 0; i--) {
+    f += sum - numsSize * nums[i];
+    ans = fmax(ans, f);
+  }
+  return ans;
+}
+
+int main() {
+  int n1[] = {4, 3, 2, 6}, n2[] = {100};
+  int r1 = maxRotateFunction(n1, ARRAY_SIZE(n1));
+  int r2 = maxRotateFunction(n2, ARRAY_SIZE(n2));
+  printf("%d\n", r1);
+  assert(r1 == 26);
+  printf("%d\n", r2);
+  assert(r2 == 0);
+}
diff --git a/rotate_function.py b/rotate_function.py
@@ -0,0 +1,29 @@
+# 396. Rotate Function
+from typing import List
+
+"""
+you are given an integer array 'nums' of length 'n'. assume 'arr_k' to be an
+array obtained by rotating 'nums' by 'k' positions clockwise. we define the
+rotation function 'F' on 'nums' as follows: 'F(k) = 0  arr_k[0] + 1
+arr_k[1] + ... + (n - 1)  arr_k[n - 1]'. return the maximum value of 'F(0),
+F(1), ..., F(n - 1)'. the test cases are generated such that the answer fits
+in a 32-bit integer.
+"""
+
+
+class Solution:
+    def maxRotateFunction(self, nums: List[int]) -> int:
+        f, n, total = 0, len(nums), sum(nums)
+        for i, j in enumerate(nums):
+            f += i * j
+        ans = f
+        for i in range(n - 1, 0, -1):
+            f += total - n * nums[i]
+            ans = max(ans, f)
+        return ans
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    print(obj.maxRotateFunction(nums=[4, 3, 2, 6]))
+    print(obj.maxRotateFunction(nums=[100]))