643. Maximum Average Subarray I

Easy (Dễ) C++ 🔗 Xem trên LeetCode

📋 Đề Bài

You are given an integer array nums consisting of n elements, and an integer k.

Find a contiguous subarray whose length is equal to k that has the maximum average value and return this value. Any answer with a calculation error less than 10-5 will be accepted.

 

Example 1:

Input: nums = [1,12,-5,-6,50,3], k = 4
Output: 12.75000
Explanation: Maximum average is (12 - 5 - 6 + 50) / 4 = 51 / 4 = 12.75

Example 2:

Input: nums = [5], k = 1
Output: 5.00000

 

Constraints:

  • n == nums.length
  • 1 <= k <= n <= 105
  • -104 <= nums[i] <= 104

💻 Lời Giải

C++ 0643-maximum-average-subarray-i.cpp 
class Solution {
public:
    double findMaxAverage(vector<int>& nums, int k) {
        const int n = nums.size();
        int sum = 0, maxSum = INT_MIN;
        
        for (int i = 0; i < k; ++i) {
            sum += nums[i];
        }
        
        maxSum = max(maxSum, sum);
        
        for (int i = k; i < n; ++i) {
            sum += nums[i] - nums[i - k];
            maxSum = max(maxSum, sum);
        }
        
        return maxSum*1.0/k;
    }
};