cmpstr/dist/cjs/metric/LCS.cjs

CmpStr is a lightweight, fast and well performing package for calculating string similarity

// CmpStr v3.2.2 build-bb61120-260311 by Paul Köhler @komed3 / MIT License
'use strict';

var Pool = require('../utils/Pool.cjs');
var Metric = require('./Metric.cjs');

class LCSMetric extends Metric.Metric {
  constructor(a, b, opt = {}) {
    super('lcs', a, b, opt, true);
  }
  compute(a, b, m, n, maxLen) {
    const len = m + 1;
    const [prev, curr] = Pool.Pool.acquireMany('int32', [len, len]);
    try {
      for (let i = 0; i <= m; i++) prev[i] = 0;
      for (let j = 1; j <= n; j++) {
        curr[0] = 0;
        const cb = b.charCodeAt(j - 1);
        for (let i = 1; i <= m; i++) {
          if (a.charCodeAt(i - 1) === cb) curr[i] = prev[i - 1] + 1;
          else curr[i] = Math.max(prev[i], curr[i - 1]);
        }
        prev.set(curr);
      }
      const lcs = prev[m];
      return {
        res: maxLen === 0 ? 1 : Metric.Metric.clamp(lcs / maxLen),
        raw: { lcs, maxLen }
      };
    } finally {
      Pool.Pool.release('int32', prev, len);
      Pool.Pool.release('int32', curr, len);
    }
  }
}
Metric.MetricRegistry.add('lcs', LCSMetric);

exports.LCSMetric = LCSMetric;