[Leetcode] 643. Maximum Average Subarray I 解题报告

题目

Given an array consisting of n integers, find the contiguous subarray of given length k that has the maximum average value. And you need to output the maximum average value.

Example 1:

Input: [1,12,-5,-6,50,3], k = 4
Output: 12.75
Explanation: Maximum average is (12-5-6+50)/4 = 51/4 = 12.75

Note:

  1. 1 <= k <= n <= 30,000.
  2. Elements of the given array will be in the range [-10,000, 10,000].

思路

一道简单的移动窗口问题。我们只需要记录最大的区间和,最后除以k即可。

代码

class Solution {
public:
    double findMaxAverage(vector<int>& nums, int k) {
        double sum = 0, max_sum = INT_MIN;
        for (int i = 0; i < nums.size(); ++i) {
            if (i < k) {
                sum += nums[i];
            }
            else {
                max_sum = max(max_sum, sum);
                sum += nums[i] - nums[i - k];
            }
        }
        max_sum = max(max_sum, sum);
        return max_sum / k;
    }
};
;