LeetCode 3427: Sum of Variable Length Subarrays Solution

Master LeetCode problem 3427 (Sum of Variable Length Subarrays), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

3427. Sum of Variable Length Subarrays

Easy

Array Prefix Sum

Problem Explanation

Explanation

To solve this problem, we need to calculate the sum of all possible subarrays for each index i in the given array nums. The key observation is that for each index i, the start index of the subarray can be calculated as start = max(0, i - nums[i]). We then iterate through all possible subarrays and calculate the sum.

Algorithm:

Initialize a variable totalSum to 0 to store the total sum of all subarrays.
Iterate over each index i in the array nums.
Calculate the start index as start = max(0, i - nums[i]).
Iterate over the subarray from indices start to i and calculate the sum by adding each element to totalSum.
Finally, return totalSum as the result.

Time Complexity: O(n^2) where n is the number of elements in the array nums. Space Complexity: O(1) as we are using only a constant amount of extra space.

Solution Code

class Solution {
    public int sumOfSubarrays(int[] nums) {
        int totalSum = 0;
        for (int i = 0; i < nums.length; i++) {
            int start = Math.max(0, i - nums[i]);
            for (int j = start; j <= i; j++) {
                totalSum += nums[j];
            }
        }
        return totalSum;
    }
}

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