643. Maximum Average Subarray I

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].

 

Rust Solution

struct Solution;

impl Solution {
    fn find_max_average(nums: Vec<i32>, k: i32) -> f64 {
        let mut sum = 0;
        let k = k as usize;
        let n = nums.len();
        for i in 0..k {
            sum += nums[i];
        }
        let mut max = sum;
        for i in k..n {
            sum += nums[i];
            sum -= nums[i - k];
            max = i32::max(sum, max);
        }
        max as f64 / k as f64
    }
}

#[test]
fn test() {
    use assert_approx_eq::assert_approx_eq;
    let nums = vec![1, 12, -5, -6, 50, 3];
    let k = 4;
    assert_approx_eq!(Solution::find_max_average(nums, k), 12.75);
}

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