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fix longestCommonSubstring() to handle unicode characters (#129) (#176)

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DADDOU Mohamed El Amine 2018-08-28 05:56:44 +02:00 committed by Oleksii Trekhleb
parent e09d526785
commit 82ac89b16a
2 changed files with 12 additions and 8 deletions
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1
src/algorithms/string/longest-common-substring/__test__/longestCommonSubstring.test.js
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@ -7,5 +7,6 @@ describe('longestCommonSubstring', () => {
expect(longestCommonSubstring('', 'ABC')).toBe('');
expect(longestCommonSubstring('ABABC', 'BABCA')).toBe('BABC');
expect(longestCommonSubstring('BABCA', 'ABCBA')).toBe('ABC');
expect(longestCommonSubstring('𐌵𐌵**ABC', '𐌵𐌵--ABC')).toBe('ABC');
});
});

19
src/algorithms/string/longest-common-substring/longestCommonSubstring.js
View File

@ -4,17 +4,20 @@
* @return {string}
*/
export default function longestCommonSubstring(s1, s2) {
// transform s1 & s2 into arrays to allow handling unicodes as single caracter.
const [a1, a2] = [s1, s2].map(s => Array.from(s));
// Init the matrix of all substring lengths to use Dynamic Programming approach.
const substringMatrix = Array(s2.length + 1).fill(null).map(() => {
return Array(s1.length + 1).fill(null);
const substringMatrix = Array(a2.length + 1).fill(null).map(() => {
return Array(a1.length + 1).fill(null);
});
// Fill the first row and first column with zeros to provide initial values.
for (let columnIndex = 0; columnIndex <= s1.length; columnIndex += 1) {
for (let columnIndex = 0; columnIndex <= a1.length; columnIndex += 1) {
substringMatrix[0][columnIndex] = 0;
}
for (let rowIndex = 0; rowIndex <= s2.length; rowIndex += 1) {
for (let rowIndex = 0; rowIndex <= a2.length; rowIndex += 1) {
substringMatrix[rowIndex][0] = 0;
}
@ -23,9 +26,9 @@ export default function longestCommonSubstring(s1, s2) {
let longestSubstringColumn = 0;
let longestSubstringRow = 0;
for (let rowIndex = 1; rowIndex <= s2.length; rowIndex += 1) {
for (let columnIndex = 1; columnIndex <= s1.length; columnIndex += 1) {
if (s1[columnIndex - 1] === s2[rowIndex - 1]) {
for (let rowIndex = 1; rowIndex <= a2.length; rowIndex += 1) {
for (let columnIndex = 1; columnIndex <= a1.length; columnIndex += 1) {
if (a1[columnIndex - 1] === a2[rowIndex - 1]) {
substringMatrix[rowIndex][columnIndex] = substringMatrix[rowIndex - 1][columnIndex - 1] + 1;
} else {
substringMatrix[rowIndex][columnIndex] = 0;
@ -50,7 +53,7 @@ export default function longestCommonSubstring(s1, s2) {
let longestSubstring = '';
while (substringMatrix[longestSubstringRow][longestSubstringColumn] > 0) {
longestSubstring = s1[longestSubstringColumn - 1] + longestSubstring;
longestSubstring = a1[longestSubstringColumn - 1] + longestSubstring;
longestSubstringRow -= 1;
longestSubstringColumn -= 1;
}