Longest Ordered Subsequence With a Fixed Step

### Problem Choose a subsequence of arr without reordering its elements. Every adjacent pair in the chosen sequence must increase by exactly difference, which may be negative or zero. Return its maximum length. ```cpp class Solution { public: int longestSubsequence(vector<int>& arr, int difference); }; ``` ### Examples **Example 1:** ```text Input: arr = [5,3,4,1], difference = -2 Output: 3 Explanation: The subsequence5,3,1 has the required step and retains input order. ``` **Example 2:** ```text Input: arr = [2,2,1,2], difference = 0 Output: 3 Explanation: Select all three occurrences of2. ``` ### Constraints - The array contains 1 to 100000 integers. - Both each value and difference lie in `[-10000,10000]`. ### Contract considerations Return a subsequence length, with the original element order preserved. ```hint Read the boundary condition When difference is zero or negative, must a valid subsequence still preserve the original element order? ``` ### Boundary reminders Return a subsequence length, with the original element order preserved.