# Subarrays Distinct Element Sum of Squares II Solution Leetcode

## Subarrays Distinct Element Sum of Squares II Solution Leetcode

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• Difficulty:Hard

You are given a 0-indexed integer array `nums`.

The distinct count of a subarray of `nums` is defined as:

• Let `nums[i..j]` be a subarray of `nums` consisting of all the indices from `i` to `j` such that `0 <= i <= j < nums.length`. Then the number of distinct values in `nums[i..j]` is called the distinct count of `nums[i..j]`.

Return the sum of the squares of distinct counts of all subarrays of `nums`.

Since the answer may be very large, return it modulo `109 + 7`.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

```Input: nums = [1,2,1]
Output: 15
Explanation: Six possible subarrays are:
[1]: 1 distinct value
[2]: 1 distinct value
[1]: 1 distinct value
[1,2]: 2 distinct values
[2,1]: 2 distinct values
[1,2,1]: 2 distinct values
The sum of the squares of the distinct counts in all subarrays is equal to 12 + 12 + 12 + 22 + 22 + 22 = 15.
```

Example 2:

```Input: nums = [2,2]
Output: 3
Explanation: Three possible subarrays are:
[2]: 1 distinct value
[2]: 1 distinct value
[2,2]: 1 distinct value
The sum of the squares of the distinct counts in all subarrays is equal to 12 + 12 + 12 = 3.```

Constraints:

• `1 <= nums.length <= 105`
• `1 <= nums[i] <= 105`