Leetcode 2407 Longest Increasing Subsequence II Solution in Java | Hindi Coding Community

 

You are given an integer array nums and an integer k.

Find the longest subsequence of nums that meets the following requirements:

• The subsequence is strictly increasing and
• The difference between adjacent elements in the subsequence is at most k.

Return the length of the longest subsequence that meets the requirements.

A subsequence is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.

 

Example 1:

Input: nums = [4,2,1,4,3,4,5,8,15], k = 3
Output: 5
Explanation:
The longest subsequence that meets the requirements is [1,3,4,5,8].
The subsequence has a length of 5, so we return 5.
Note that the subsequence [1,3,4,5,8,15] does not meet the requirements because 15 - 8 = 7 is larger than 3.

Example 2:

Input: nums = [7,4,5,1,8,12,4,7], k = 5
Output: 4
Explanation:
The longest subsequence that meets the requirements is [4,5,8,12].
The subsequence has a length of 4, so we return 4.

Example 3:

Input: nums = [1,5], k = 1
Output: 1
Explanation:
The longest subsequence that meets the requirements is [1].
The subsequence has a length of 1, so we return 1.

 

Constraints:

• 1 <= nums.length <= 105
• 1 <= nums[i], k <= 105

Java Code :

class Solution {

int N = 100001;

int[] seg = new int[2*N];

void update(int pos, int val){ // update max

pos += N;

seg[pos] = val;

while (pos > 1) {

pos >>= 1;

seg[pos] = Math.max(seg[2*pos], seg[2*pos+1]);

}

}

int query(int lo, int hi){

lo += N;

hi += N;

int res = 0;

while (lo < hi) {

if ((lo & 1)==1) {

res = Math.max(res, seg[lo++]);

}

if ((hi & 1)==1) {

res = Math.max(res, seg[--hi]);

}

lo >>= 1;

hi >>= 1;

}

return res;

}

public int lengthOfLIS(int[] A, int k) {

int ans = 0;

for (int i = 0; i < A.length; ++i){

int l = Math.max(0, A[i]-k);

int r = A[i];

int res = query(l, r) + 1;

ans = Math.max(res, ans);

update(A[i], res);

}

return ans;

}

}