[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 <= 

k

 <= 

n

 <=
30,000.
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;
}
};