## 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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