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77 lines
1.7 KiB
77 lines
1.7 KiB
'use strict'; |
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const array = []; |
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const charCodeCache = []; |
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const leven = (left, right) => { |
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if (left === right) { |
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return 0; |
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} |
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const swap = left; |
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// Swapping the strings if `a` is longer than `b` so we know which one is the |
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// shortest & which one is the longest |
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if (left.length > right.length) { |
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left = right; |
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right = swap; |
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} |
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let leftLength = left.length; |
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let rightLength = right.length; |
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// Performing suffix trimming: |
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// We can linearly drop suffix common to both strings since they |
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// don't increase distance at all |
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// Note: `~-` is the bitwise way to perform a `- 1` operation |
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while (leftLength > 0 && (left.charCodeAt(~-leftLength) === right.charCodeAt(~-rightLength))) { |
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leftLength--; |
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rightLength--; |
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} |
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// Performing prefix trimming |
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// We can linearly drop prefix common to both strings since they |
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// don't increase distance at all |
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let start = 0; |
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while (start < leftLength && (left.charCodeAt(start) === right.charCodeAt(start))) { |
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start++; |
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} |
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leftLength -= start; |
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rightLength -= start; |
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if (leftLength === 0) { |
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return rightLength; |
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} |
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let bCharCode; |
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let result; |
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let temp; |
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let temp2; |
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let i = 0; |
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let j = 0; |
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while (i < leftLength) { |
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charCodeCache[i] = left.charCodeAt(start + i); |
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array[i] = ++i; |
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} |
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while (j < rightLength) { |
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bCharCode = right.charCodeAt(start + j); |
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temp = j++; |
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result = j; |
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for (i = 0; i < leftLength; i++) { |
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temp2 = bCharCode === charCodeCache[i] ? temp : temp + 1; |
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temp = array[i]; |
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// eslint-disable-next-line no-multi-assign |
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result = array[i] = temp > result ? temp2 > result ? result + 1 : temp2 : temp2 > temp ? temp + 1 : temp2; |
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} |
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} |
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return result; |
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}; |
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module.exports = leven; |
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// TODO: Remove this for the next major release |
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module.exports.default = leven;
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