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Commit c9f1caf

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Add a recursive version of the Longest Common Substring.
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4 files changed

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4 files changed

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‎src/algorithms/string/longest-common-substring/__test__/longestCommonSubstring.test.js‎

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@@ -7,6 +7,8 @@ describe('longestCommonSubstring', () => {
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expect(longestCommonSubstring('', 'ABC')).toBe('');
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expect(longestCommonSubstring('ABABC', 'BABCA')).toBe('BABC');
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expect(longestCommonSubstring('BABCA', 'ABCBA')).toBe('ABC');
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expect(longestCommonSubstring('sea', 'eat')).toBe('ea');
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expect(longestCommonSubstring('algorithms', 'rithm')).toBe('rithm');
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expect(longestCommonSubstring(
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'Algorithms and data structures implemented in JavaScript',
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'Here you may find Algorithms and data structures that are implemented in JavaScript',
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import longestCommonSubstring from '../longestCommonSubstringRecursive';
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describe('longestCommonSubstringRecursive', () => {
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it('should find longest common substring between two strings', () => {
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expect(longestCommonSubstring('', '')).toBe('');
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expect(longestCommonSubstring('ABC', '')).toBe('');
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expect(longestCommonSubstring('', 'ABC')).toBe('');
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expect(longestCommonSubstring('ABABC', 'BABCA')).toBe('BABC');
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expect(longestCommonSubstring('BABCA', 'ABCBA')).toBe('ABCA');
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expect(longestCommonSubstring('sea', 'eat')).toBe('ea');
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expect(longestCommonSubstring('algorithms', 'rithm')).toBe('rithm');
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expect(longestCommonSubstring(
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'Algorithms and data structures implemented in JavaScript',
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'Here you may find Algorithms and data structures that are implemented in JavaScript',
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)).toBe('Algorithms and data structures implemented in JavaScript');
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});
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});

‎src/algorithms/string/longest-common-substring/longestCommonSubstring.js‎

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/**
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* Longest Common Substring (LCS) (Dynamic Programming Approach).
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*
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* @param {string} string1
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* @param {string} string2
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* @return {string}
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/* eslint-disable no-param-reassign */
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/**
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* Longest Common Substring (LCS) (Recursive Approach).
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*
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* @param {string} string1
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* @param {string} string2
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* @return {number}
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*/
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export default function longestCommonSubstringRecursive(string1, string2) {
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/**
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*
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* @param {string} s1
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* @param {string} s2
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* @return {string} - returns the LCS (Longest Common Substring)
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*/
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const lcs = (s1, s2, memo = {}) => {
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if (!s1 || !s2) return '';
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if (memo[`${s1}:${s2}`]) return memo[`${s1}:${s2}`];
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if (s1[0] === s2[0]) {
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return s1[0] + lcs(s1.substring(1), s2.substring(1), memo);
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}
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const nextLcs1 = lcs(s1.substring(1), s2, memo);
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const nextLcs2 = lcs(s1, s2.substring(1), memo);
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const nextLongest = nextLcs1.length >= nextLcs2.length ? nextLcs1 : nextLcs2;
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memo[`${s1}:${s2}`] = nextLongest;
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return nextLongest;
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};
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return lcs(string1, string2);
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}

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