3731. Sum of Variable Length Subarrays

Easy

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You are given an integer array nums of size n. For each index i where 0 <= i < n, define a subarray nums[start ... i] where start = max(0, i - nums[i]).

Return the total sum of all elements from the subarray defined for each index in the array.

 

Example 1:

Input: nums = [2,3,1]

Output: 11

Explanation:

i	Subarray	Sum
0	nums[0] = [2]	2
1	nums[0 ... 1] = [2, 3]	5
2	nums[1 ... 2] = [3, 1]	4
Total Sum		11

The total sum is 11. Hence, 11 is the output.

Example 2:

Input: nums = [3,1,1,2]

Output: 13

Explanation:

i	Subarray	Sum
0	nums[0] = [3]	3
1	nums[0 ... 1] = [3, 1]	4
2	nums[1 ... 2] = [1, 1]	2
3	nums[1 ... 3] = [1, 1, 2]	4
Total Sum		13

The total sum is 13. Hence, 13 is the output.

 

Constraints:

• 1 <= n == nums.length <= 100
• 1 <= nums[i] <= 1000