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-rw-r--r--longest_arithmetic_subseq_diff.cpp33
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diff --git a/longest_arithmetic_subseq_diff.cpp b/longest_arithmetic_subseq_diff.cpp
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-// 1218. Longest Arithmetic Subsequence of Given Difference
-#include "leetcode.h"
-
-/*
- * given an integer array 'arr' and an integer 'difference', return the length
- * of the longest subsequence in 'arr' which is an arithmetic sequence such that
- * the difference between adjacent elements in the subsequence equals
- * 'difference'. a subsequence is a sequence that can be derived from 'arr' by
- * deleting some or no elements without changing the order of the remaining
- * elements.
- */
-
-class Solution {
-public:
- int longestSubsequence(vector<int> &arr, int difference) {
- int ans = 1;
- unordered_map<int, int> max;
- for (int i = 0; i < arr.size(); i++)
- max[arr[i]] = max[arr[i] - difference] + 1;
- for (auto i : max)
- ans = std::max(ans, i.second);
- return ans;
- }
-};
-
-int main() {
- Solution obj;
- vector<int> a1 = {1, 2, 3, 4}, a2 = {1, 3, 5, 7},
- a3 = {1, 5, 7, 8, 5, 3, 4, 2, 1};
- printf("%d\n", obj.longestSubsequence(a1, 1)); // expect: 4
- printf("%d\n", obj.longestSubsequence(a2, 1)); // expect: 1
- printf("%d\n", obj.longestSubsequence(a3, -2)); // expect: 4
-}