_643.java

package com.fishercoder.solutions;

/**
 * 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 <= k <= n <= 30,000.
 Elements of the given array will be in the range [-10,000, 10,000].
 */
public class _643 {

    public static double findMaxAverage(int[] nums, int k) {
        double sum = 0;
        double maxAve = Integer.MIN_VALUE;
        for (int i = 0; i < nums.length; i++) {
            if (k <= i) {
                sum -= nums[i - k];
            }
            sum += nums[i];
            if ((i + 1) >= k) {
                maxAve = Math.max(maxAve, sum / k);
            }
        }
        return maxAve;
    }

    public static void main(String... args) {
//        int[] nums = new int[]{1,12,-5,-6,50,3};
//        int k = 4;

//        int[] nums = new int[]{-1};
//        int k = 1;

        int[] nums = new int[]{-6662, 5432, -8558, -8935, 8731, -3083, 4115, 9931, -4006, -3284, -3024, 1714, -2825, -2374, -2750, -959, 6516, 9356, 8040, -2169, -9490, -3068, 6299, 7823, -9767, 5751, -7897, 6680, -1293, -3486, -6785, 6337, -9158, -4183, 6240, -2846, -2588, -5458, -9576, -1501, -908, -5477, 7596, -8863, -4088, 7922, 8231, -4928, 7636, -3994, -243, -1327, 8425, -3468, -4218, -364, 4257, 5690, 1035, 6217, 8880, 4127, -6299, -1831, 2854, -4498, -6983, -677, 2216, -1938, 3348, 4099, 3591, 9076, 942, 4571, -4200, 7271, -6920, -1886, 662, 7844, 3658, -6562, -2106, -296, -3280, 8909, -8352, -9413, 3513, 1352, -8825};
        int k = 90;
        System.out.println(findMaxAverage(nums, k));
    }
}