446. Arithmetic Slices II - Subsequence Hard

1/**
2 * [446] Arithmetic Slices II - Subsequence
3 *
4 * Given an integer array nums, return the number of all the arithmetic subsequences of nums.
5 * 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.
6 * 
7 * 	For example, [1, 3, 5, 7, 9], [7, 7, 7, 7], and [3, -1, -5, -9] are arithmetic sequences.
8 * 	For example, [1, 1, 2, 5, 7] is not an arithmetic sequence.
9 * 
10 * A subsequence of an array is a sequence that can be formed by removing some elements (possibly none) of the array.
11 * 
12 * 	For example, [2,5,10] is a subsequence of [1,2,1,<u>2</u>,4,1,<u>5</u>,<u>10</u>].
13 * 
14 * The test cases are generated so that the answer fits in 32-bit integer.
15 *  
16 * Example 1:
17 * 
18 * Input: nums = [2,4,6,8,10]
19 * Output: 7
20 * Explanation: All arithmetic subsequence slices are:
21 * [2,4,6]
22 * [4,6,8]
23 * [6,8,10]
24 * [2,4,6,8]
25 * [4,6,8,10]
26 * [2,4,6,8,10]
27 * [2,6,10]
28 * 
29 * Example 2:
30 * 
31 * Input: nums = [7,7,7,7,7]
32 * Output: 16
33 * Explanation: Any subsequence of this array is arithmetic.
34 * 
35 *  
36 * Constraints:
37 * 
38 * 	1  <= nums.length <= 1000
39 * 	-2^31 <= nums[i] <= 2^31 - 1
40 * 
41 */
42pub struct Solution {}
43
44// problem: https://leetcode.com/problems/arithmetic-slices-ii-subsequence/
45// discuss: https://leetcode.com/problems/arithmetic-slices-ii-subsequence/discuss/?currentPage=1&orderBy=most_votes&query=
46
47// submission codes start here
48
49impl Solution {
50    pub fn number_of_arithmetic_slices(nums: Vec<i32>) -> i32 {
51        0
52    }
53}
54
55// submission codes end
56
57#[cfg(test)]
58mod tests {
59    use super::*;
60
61    #[test]
62    fn test_446() {
63    }
64}
65