643. Maximum Average Subarray I

Description

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].

Solution

Sliding window, time O(n), space O(1)

这道被我鄙视的题，我竟然写错了...敬畏敬畏...

class Solution {
    public double findMaxAverage(int[] nums, int k) {
        double sum = 0;
        for (int i = 0; i < k; ++i) {
            sum += nums[i];
        }
        
        double maxSum = sum;
        for (int i = k; i < nums.length; ++i) {
            sum += nums[i] - nums[i - k];
            maxSum = Math.max(maxSum, sum);
        }
        
        return maxSum / k;
    }
}