396. 旋转函数

Author: w2xi

README.md

@@ -72,6 +72,7 @@
 |349|[两个数组的交集](https://leetcode-cn.com/problems/intersection-of-two-arrays/)|[JavaScript](./algorithms/intersection-of-two-arrays.js)|Easy|
 |350|[两个数组的交集 II](https://leetcode-cn.com/problems/intersection-of-two-arrays-ii/)|[JavaScript](./algorithms/intersection-of-two-arrays-ii.js)|Easy|
 |387|[字符串中的第一个唯一字符](https://leetcode-cn.com/problems/first-unique-character-in-a-string/)|[JavaScript](./algorithms/first-unique-character-in-a-string.js)|Easy|
+|396|[旋转函数](https://leetcode.cn/problems/rotate-function/)|[JavaScript](./algorithms/rotate-function.js)|Medium|
 |404|[左叶子之和](https://leetcode.cn/problems/sum-of-left-leaves/)|[JavaScript](./algorithms/sum-of-left-leaves.js)|Easy|
 |414|[第三大的数](https://leetcode.cn/problems/third-maximum-number/)|[JavaScript](./algorithms/third-maximum-number.js)|Easy|
 |442|[数组中重复的数据](https://leetcode.cn/problems/find-all-duplicates-in-an-array/)|[JavaScript](./algorithms/find-all-duplicates-in-an-array.js)|Medium|

algorithms/rotate-function.js

@@ -0,0 +1,25 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+ var maxRotateFunction = function(nums) {
+  // 参考: https://leetcode.cn/problems/rotate-function/solution/by-ac_oier-sxbi/
+  
+  let n = nums.length;
+  let sum = 0;
+  let f = 0, ans = 0;
+
+  for (let i = 0; i < n; i++) {
+      sum += nums[i];   // 计算 sum
+      f += i * nums[i]; // 计算 F(0)
+  }
+  
+  ans = f;
+  
+  for (let i = 1; i < n; i++) {      // 迭代计算 F(i)
+      f = f + sum - n * nums[n - i]; // F(i) = F(i-1) + sum - n * A(n-i)
+      ans = Math.max(ans, f);
+  }
+
+  return ans;
+};