LeetCode 솔루션 분류
1027. Longest Arithmetic Subsequence
본문
https://leetcode.com/problems/longest-arithmetic-subsequence/
Given an array nums of integers, return the length of the longest arithmetic subsequence in nums.
Recall that a subsequence of an array nums is a list nums[i1], nums[i2], ..., nums[ik] with 0 <= i1 < i2 < ... < ik <= nums.length - 1, and that a sequence seq is arithmetic if seq[i+1] - seq[i] are all the same value (for 0 <= i < seq.length - 1).
Example 1:
Input: nums = [3,6,9,12] Output: 4 Explanation: The whole array is an arithmetic sequence with steps of length = 3.
Example 2:
Input: nums = [9,4,7,2,10] Output: 3 Explanation: The longest arithmetic subsequence is [4,7,10].
Example 3:
Input: nums = [20,1,15,3,10,5,8] Output: 4 Explanation: The longest arithmetic subsequence is [20,15,10,5].
Constraints:
2 <= nums.length <= 10000 <= nums[i] <= 500
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class Solution {
public int longestArithSeqLength(int[] nums) {
int[][] dp = new int[1001][1001];
int n = nums.length;
int maxLength = 1;
// 3 6 9 12
for(int i=1; i<n; i++){
for(int j=0; j<i; j++){
int diff = nums[i] - nums[j] + 500; // 500 is a complement from input
dp[i][diff] = Math.max(dp[i][diff], dp[j][diff] + 1);
maxLength = Math.max(maxLength, dp[i][diff]);
}
}
return maxLength + 1;
}
}
