Test

top10tuples.js

// Here is our log file; essentially a list of tuples.
// Each tuple has two items: `(request_path, user_id)`
const logFile = [
  ["/", "user_1"],
  ["/about", "user_1"],
  ["/", "user_3"],
  ["/features", "user_1"],
  ["/about", "user_2"],
  ["/purchase", "user_2"],
  ["/purchase", "user_1"],
  ["/thank-you", "user_1"],
  ["/about", "user_3"],
  ["/thank-you", "user_2"],
  ["/purchase", "user_3"],
  ["/thank-you", "user_3"]
];

// A triplet is a group of three consecutive pages visited by the same user. For example,
// user_1 visited the following pages in this order:
//    '/' , '/about', '/features', '/purchase', '/thank-you'
//
// In this case, user_1 created three unique triplets during her visit:
//    1. ['/', '/about', '/features']
//    2. ['/about', '/features', '/purchase']
//    3. ['/features', '/purchase', '/thank-you']
//
// At the same time, user_3 went through a different workflow but created two unique triplets during his visit:
//    1. ['/', '/about', '/purchase']
//    2. ['/about', '/purchase', '/thank-you']
//
// Your function should return the 10 most occurring triplets in the log file. Given the log file above, the
// returned list should something look like:
//
// [
//    ['/about', '/purchase', '/thank-you'], // cnt 2
//    ['/', '/about', '/features'], // cnt 1
//    ['/about', '/features', '/purchase'], // cnt 1
//    ['/features', '/purchase', '/thank-you'], // cnt 1
//    ['/', '/about', '/purchase'], //cnt 1
// ]

// tuple3([0,1,2,3,4]) => [[0,1,2], [1,2,3], [2,3,4]]
const tuple3 = (arr = [], n = 3) => {
  return arr.reduce((acc, x, i) => {
    if (arr.length - n < i) {
      return acc;
    }
    const _arr = [...arr];
    const p = _arr.slice(i, i + n);
    acc.push(p);
    return acc;
  }, []);
};

const fn = (logArr = []) => {
  const group = logArr.reduce((acc, x) => {
    const [p, u] = x;
    if (!acc[u]) {
      acc[u] = [];
    }
    acc[u].push(p);
    return acc;
  }, {});

  console.trace("group", group);

  const tuples = Object.values(group)
    .map((x) => tuple3(x))
    .flat();
  console.trace("tuples", tuples);

  const top10 = tuples.reduce((acc, x) => {
    const key = JSON.stringify(x);

    if (!acc[key]) {
      acc[key] = 0;
    }

    acc[key] += 1;

    return acc;
  }, {});

  console.trace("top10", top10);

  return Object.entries(top10).sort((a, b) => b[1] - a[1]);
};

console.log("Final Result", fn(logFile));

/**
[
  [
    "[\"/about\",\"/purchase\",\"/thank-you\"]",
    2
  ],
  [
    "[\"/\",\"/about\",\"/features\"]",
    1
  ],
  [
    "[\"/about\",\"/features\",\"/purchase\"]",
    1
  ],
  [
    "[\"/features\",\"/purchase\",\"/thank-you\"]",
    1
  ],
  [
    "[\"/\",\"/about\",\"/purchase\"]",
    1
  ]
]

*/