Codeforces 977F Consecutive Subsequence - Problem Statement

As the next DP problem from Codeforces, solve "Consecutive Subsequence". This problem shows how the same four-step DP pattern works even when the values in the array are large.

You are given a sequence $a_1, a_2, \dots, a_n$. find a subsequence (delete some elements, but you must keep the order) such that consecutive elements in the subsequence differ by exactly one. for indices of any subsequence $i_1, i_2, \dots , i_k$ you want $a_{i_{j+1}} = a_{i_j} + 1$ Every $j$.

Among all such subsequences, you want the one with maximum length. You have to output the maximum length and the indices of the subsequence with the maximum length.

Constraints: $1 \le n \le 2 \cdot 10^5$ $1 \le a[i] \le 10^9$