LongestDecreasingSubsequence

The length of a longest decreasing subsequence.

WikipediaLongest increasing subsequence↗WikidataQ4183855↗

LongestDecreasingSubsequence(p)

Domain: Permutation statistics

Details

• Defined over `Permutation` as an expression in `_x`, evaluated by compute-engine — the definition IS the implementation.
• Takes a `Permutation`, and also a bare list of integers: this reading compares entries with each other rather than with their positions, so it stands on any sequence.
• The same fold with the comparison reversed — by Dilworth, the number of piles when the tops are kept decreasing.

Examples