Adds Longest Arithmetic Subsequence Implementation (#5501)

* Added LongestArthmeticSubsequence

---------

Co-authored-by: Piotr Idzik <65706193+vil02@users.noreply.github.com>
This commit is contained in:
Tejaswi Tyagi
2024-10-03 18:34:49 +05:30
committed by GitHub
parent 48a298028d
commit be8df2188c
2 changed files with 77 additions and 0 deletions

View File

@ -0,0 +1,42 @@
package com.thealgorithms.dynamicprogramming;
import java.util.HashMap;
final class LongestArithmeticSubsequence {
private LongestArithmeticSubsequence() {
}
/**
* Returns the length of the longest arithmetic subsequence in the given array.
*
* A sequence seq is arithmetic if seq[i + 1] - seq[i] are all the same value
* (for 0 <= i < seq.length - 1).
*
* @param nums the input array of integers
* @return the length of the longest arithmetic subsequence
*/
public static int getLongestArithmeticSubsequenceLength(int[] nums) {
if (nums == null) {
throw new IllegalArgumentException("Input array cannot be null");
}
if (nums.length <= 1) {
return nums.length;
}
HashMap<Integer, Integer>[] dp = new HashMap[nums.length];
int maxLength = 2;
// fill the dp array
for (int i = 0; i < nums.length; i++) {
dp[i] = new HashMap<>();
for (int j = 0; j < i; j++) {
final int diff = nums[i] - nums[j];
dp[i].put(diff, dp[j].getOrDefault(diff, 1) + 1);
maxLength = Math.max(maxLength, dp[i].get(diff));
}
}
return maxLength;
}
}