Sequence LCS

sequence-lcs · version 1.0.0 · Sequences & diffs · free, no key needed

Compute the longest common subsequence of two bounded sequences from the Myers shortest edit script.

Use when you need to: sequence lcs · longest common subsequence of two sequences · sequence longest common subsequence.

Supported

• sequence lcs
• longest common subsequence of two sequences
• sequence longest common subsequence

Not supported

• longest common substring
• fuzzy matching
• unicode normalization
• patience diff
• histogram diff
• locale compare

Behavior

• left and right are sequences of JSON null, boolean, string, or IEEE-754 safe integer items.
• Item equality is JavaScript === after validation; there is no case folding, locale compare, or Unicode normalization.
• The LCS is the keep-op values of the Myers shortest edit script, in left order, with parallel index arrays.
• When two Myers D-paths tie, the library prefers a delete from the left sequence.
• For left ["A","B"] and right ["B","A"] the LCS is ["B"] with left_indices [1] and right_indices [0].
• length equals items.length. Empty sequences yield empty arrays and length 0.
• The string "__proto__" is an ordinary item. Unknown input fields are rejected.

Input

• left (array of null or boolean or string or integer, required): max items 1024
• right (array of null or boolean or string or integer, required): max items 1024

Output

• items (array of null or boolean or string or integer, required): max items 1024
• left_indices (array of integer, required): each min 0
• right_indices (array of integer, required): each min 0
• length (integer, required): min 0

Limits

• max sequence items: 1024
• max item string bytes: 4096
• max text bytes: 262144
• max output bytes: 1048576

Example

Request input:

{
  "left": [
    "A",
    "B",
    "C"
  ],
  "right": [
    "A",
    "X",
    "C"
  ]
}

Response:

{
  "result": {
    "items": [
      "A",
      "C"
    ],
    "left_indices": [
      0,
      2
    ],
    "right_indices": [
      0,
      2
    ],
    "length": 2
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "sequence-lcs",
  "version": "1.0.0",
  "input": {
    "left": [
      "A",
      "B",
      "C"
    ],
    "right": [
      "A",
      "X",
      "C"
    ]
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/sequence-lcs/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"left":["A","B","C"],"right":["A","X","C"]}'

The machine-readable contract is at /v1/tools/sequence-lcs/versions/1.0.0.

CLI

node cli.mjs run sequence-lcs 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

Related tools

• Sequence longest common substring: Find the longest contiguous common subarray of two bounded sequences.
• Sequence edit script: Compute the Myers shortest edit script between two bounded sequences, with keep/delete/insert counts.
• Sequence three way merge: Three-way merge two sequence descendants against a shared base into clean or conflict regions.
• Sequence compose edit scripts: Compose two sequence edit scripts into one per-item keep/delete/insert script.
• Sequence apply edit script: Apply a keep/delete/insert edit script to a bounded sequence with exact value matching and no fuzz.
• Sequence apply hunks: Apply disjoint original-address sequence hunks with exact context and no fuzz.