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levenshteinDistance.js
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levenshteinDistance.js
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/**
* @param {string} a
* @param {string} b
* @return {number}
*/
export default function levenshteinDistance(a, b) {
// Create empty edit distance matrix for all possible modifications of
// substrings of a to substrings of b.
const distanceMatrix = Array(b.length + 1).fill(null).map(() => Array(a.length + 1).fill(null));
// Fill the first row of the matrix.
// If this is first row then we're transforming empty string to a.
// In this case the number of transformations equals to size of a substring.
for (let i = 0; i <= a.length; i += 1) {
distanceMatrix[0][i] = i;
}
// Fill the first column of the matrix.
// If this is first column then we're transforming empty string to b.
// In this case the number of transformations equals to size of b substring.
for (let j = 0; j <= b.length; j += 1) {
distanceMatrix[j][0] = j;
}
for (let j = 1; j <= b.length; j += 1) {
for (let i = 1; i <= a.length; i += 1) {
const indicator = a[i - 1] === b[j - 1] ? 0 : 1;
distanceMatrix[j][i] = Math.min(
distanceMatrix[j][i - 1] + 1, // deletion
distanceMatrix[j - 1][i] + 1, // insertion
distanceMatrix[j - 1][i - 1] + indicator, // substitution
);
}
}
return distanceMatrix[b.length][a.length];
}