Hard
,Array
,DP
446. Arithmetic Slices II - Subsequence
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.
[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.
[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:
Example 2:
Constraints:
1 <= nums.length <= 1000
nums[i]
<= \(2^{31} - 1\)Yen-Chi ChenSun, Nov 27, 2022 8:49 PM
Yen-Chi ChenSun, Nov 27, 2022 8:49 PM
Time: \(O(n^2)\)
Extra Space: \(O(n^2)\)