LeetCode 643. Maximum Average Subarray I

from typing import List


class Solution:
    def findMaxAverage(self, nums: List[int], k: int) -> float:
        curr_sum = 0
        max_sum = float('-inf')
        for i, num in enumerate(nums):
            curr_sum += num
            if i > k - 1:
                curr_sum -= nums[i - k]
            if i >= k - 1:
                max_sum = max(max_sum, curr_sum)

        return max_sum / k


if __name__ == '__main__':
    sol = Solution()
    assert sol.findMaxAverage(nums=[1, 12, -5, -6, 50, 3], k=4) == 12.75
    assert sol.findMaxAverage(nums=[5], k=1) == 5.0
    assert sol.findMaxAverage(nums=[-1], k=1) == -1

package lc

import (
	"testing"
)

func findMaxAverage(nums []int, k int) float64 {
	var currSum int
	maxSum := float64(-1 << 63) // equivalent to -infinity in float64
	for i, num := range nums {
		currSum += num // adding the current number to the sum
		if i >= k {    // when i is equal to or greater than k, subtract the leftmost number in the window from the sum
			currSum -= nums[i-k]
		}
		if i >= k-1 { // if the window size is k, update maxSum
			maxSum = max(maxSum, float64(currSum))
		}
	}
	return maxSum / float64(k)
}

func TestFindMaxAverage(t *testing.T) {
	tests := []struct {
		nums []int
		k    int
		want float64
	}{
		{[]int{1, 12, -5, -6, 50, 3}, 4, 12.75},
		{[]int{5}, 1, 5.0},
		{[]int{-1}, 1, -1.0},
	}

	for _, tt := range tests {
		got := findMaxAverage(tt.nums, tt.k)
		if got != tt.want {
			t.Errorf("findMaxAverage(%v, %v) = %v; want %v", tt.nums, tt.k, got, tt.want)
		}
	}
}