Solution (leetcode-in-java 1.19 API)

java.lang.Object
- g0401_0500.s0446_arithmetic_slices_ii_subsequence.Solution

```
public class Solution
extends Object
```
446 - Arithmetic Slices II - Subsequence.
Hard

Given an integer array nums, return the number of all the arithmetic subsequences of nums.

A sequence of numbers is called arithmetic if it consists of at least three elements and if the difference between any two consecutive elements is the same.
- For example, [1, 3, 5, 7, 9], [7, 7, 7, 7], and [3, -1, -5, -9] are arithmetic sequences.
- For example, [1, 1, 2, 5, 7] is not an arithmetic sequence.
A subsequence of an array is a sequence that can be formed by removing some elements (possibly none) of the array.
- For example, [2,5,10] is a subsequence of [1,2,1, **2** ,4,1, **5** , **10** ].
The test cases are generated so that the answer fits in 32-bit integer.

Example 1:

Input: nums = [2,4,6,8,10]

Output: 7

Explanation: All arithmetic subsequence slices are:

[2,4,6]

[4,6,8]

[6,8,10]

[2,4,6,8]

[4,6,8,10]

[2,4,6,8,10]

[2,6,10]

Example 2:

Input: nums = [7,7,7,7,7]

Output: 16

Explanation: Any subsequence of this array is arithmetic.

Constraints:
- 1 <= nums.length <= 1000
- -2³¹ <= nums[i] <= 2³¹ - 1

- Constructor Summary
  
  Constructors
  Constructor Description
  
  Solution()
- Method Summary
  
  All Methods Instance Methods Concrete Methods
  Modifier and Type Method Description
  
  int numberOfArithmeticSlices(int[] arr)
  - Methods inherited from class java.lang.Object
    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail
- Solution
```
public Solution()
```

Method Detail

numberOfArithmeticSlices

public int numberOfArithmeticSlices(int[] arr)