【LeetCode】1218. Longest Arithmetic Subsequence of Given Difference

• 2019 年 11 月 8 日
• 筆記

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本文鏈接：https://blog.csdn.net/shiliang97/article/details/102527497

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.

Example 1:

Input: arr = [1,2,3,4], difference = 1 Output: 4 Explanation: The longest arithmetic subsequence is [1,2,3,4]. Example 2:

Input: arr = [1,3,5,7], difference = 1 Output: 1 Explanation: The longest arithmetic subsequence is any single element. Example 3:

Input: arr = [1,5,7,8,5,3,4,2,1], difference = -2 Output: 4 Explanation: The longest arithmetic subsequence is [7,5,3,1].

來源：力扣（LeetCode） 鏈接：https://leetcode-cn.com/problems/longest-arithmetic-subsequence-of-given-difference 著作權歸領扣網路所有。商業轉載請聯繫官方授權，非商業轉載請註明出處。

很巧妙的演算法，但是不是我想的 枯了

class Solution {  public:      int longestSubsequence(vector<int>& arr, int difference) {          int ans=0;          map<int,int>mp;          for(auto x:arr){              ans=max(ans,mp[x]=mp[x-difference]+1);          }return ans;      }  };