freeCodeCamp/curriculum/challenges/german/10-coding-interview-prep/rosetta-code/longest-common-subsequence.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
5e6dd1278e6ca105cde40ea9	Longest common subsequence	1	385271	longest-common-subsequence

--description--

The longest common subsequence (or LCS) of groups A and B is the longest group of elements from A and B that are common between the two groups and in the same order in each group. For example, the sequences 1234 and 1224533324 have an LCS of 1234:1234 1224533324

For a string example, consider the sequences thisisatest and testing123testing. An LCS would be tsitest: thisisatest

testing123testing.

Your code only needs to deal with strings.

--instructions--

Write a case-sensitive function that returns the LCS of two strings. You don't need to show multiple LCS's.

--hints--

lcs sollte eine Funktion sein.

assert(typeof lcs == 'function');

lcs("thisisatest", "testing123testing") sollte einen String zurückgeben.

assert(typeof lcs('thisisatest', 'testing123testing') == 'string');

lcs("thisisatest", "testing123testing") sollte "tsitest" zurückgeben.

assert.equal(lcs('thisisatest', 'testing123testing'), 'tsitest');

lcs("ABCDGH", "AEDFHR") sollte "ADH" zurückgeben.

assert.equal(lcs('ABCDGH', 'AEDFHR'), 'ADH');

lcs("AGGTAB", "GXTXAYB") sollte "GTAB" zurückgeben.

assert.equal(lcs('AGGTAB', 'GXTXAYB'), 'GTAB');

lcs("BDACDB", "BDCB") sollte "BDCB" zurückgeben.

assert.equal(lcs('BDACDB', 'BDCB'), 'BDCB');

lcs("ABAZDC", "BACBAD") sollte "ABAD" zurückgeben.

assert.equal(lcs('ABAZDC', 'BACBAD'), 'ABAD');

--seed--

--seed-contents--

function lcs(a, b) {

}

--solutions--

function lcs(a, b) {
  var aSub = a.substring(0, a.length - 1);
  var bSub = b.substring(0, b.length - 1);

  if (a.length === 0 || b.length === 0) {
    return '';
  } else if (a.charAt(a.length - 1) === b.charAt(b.length - 1)) {
    return lcs(aSub, bSub) + a.charAt(a.length - 1);
  } else {
    var x = lcs(a, bSub);
    var y = lcs(aSub, b);
    return (x.length > y.length) ? x : y;
  }
}