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.
\n\n[1, 3, 5, 7, 9], [7, 7, 7, 7], and [3, -1, -5, -9] are arithmetic sequences.[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.
\n\n[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.
\n\n\n
Example 1:
\n\n\nInput: nums = [2,4,6,8,10]\nOutput: 7\nExplanation: All arithmetic subsequence slices are:\n[2,4,6]\n[4,6,8]\n[6,8,10]\n[2,4,6,8]\n[4,6,8,10]\n[2,4,6,8,10]\n[2,6,10]\n\n\n
Example 2:
\n\n\nInput: nums = [7,7,7,7,7]\nOutput: 16\nExplanation: Any subsequence of this array is arithmetic.\n\n\n
\n
Constraints:
\n\n1 <= nums.length <= 1000-231 <= nums[i] <= 231 - 1Compiled with clang 11 using the latest C++ 20 standard.
Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.
Most standard library headers are already included automatically for your convenience.
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