原题链接在这里:https://leetcode.com/problems/maximum-average-subarray-i/description/
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].
题解:
维护长度为k的sliding window的最大sum.
Time Complexity: O(nums.length). Space: O(1).
AC Java:
class Solution {
public double findMaxAverage(int[] nums, int k) {
if(nums == null || nums.length < k){
throw new IllegalArgumentException("Illegal input array length smaller than k.");
} long sum = 0;
for(int i = 0; i<k; i++){
sum += nums[i];
} long max = sum;
for(int i = k; i<nums.length; i++){
sum += nums[i]-nums[i-k];
max = Math.max(max, sum);
}
return max*1.0/k;
}
}