Codeforces 1741E Sending a Sequence - Transition Case 2

$dp[i] = \text{true}.$

Case $2.$ $L$ is at the left end of a block The block has the form $[L, x_1, x_2, \dots, x_L]$ and starts at position $i$.

• The block length is again $L + 1$.

• It covers positions $i, i + 1, \dots, i + L.$ • The prefix before this block ends at $i - 1.$ This move is valid if • $i + L \le n$ • $dp[i - 1] = \text{true}$ If both hold, then $dp[i + L] = \text{true}.$ You try both cases for every $i$ from $1$ to $n$ and update $dp$ wherever you find a valid split.