cmbn_coding_solution.ts

/**
Prompt: Given a list of session identifiers and requested paths in the form 
`[{session_id: str, path: str}, …]`, return, in descending order, 
the sessions with the most path changes, along with the number of changes for each. 
Example: 
Input
```
[
    {"session_id": "aec5075b8f0c40538f40b3ad65ac6196", "path": "/payments"}, 
    {"session_id": "aec5075b8f0c40538f40b3ad65ac6196", "path": "/upgrade"}, 
    {"session_id": "72c04277ec21427e89a71b50d58f2e0d", "path": "/details"}, 
    {"session_id": "8ec2b63530634f839b5a106888145fb8", "path": "/payments"}, 
    {"session_id": "cbd86924fdd84af885a63350a78f1c09", "path": "/details"}, 
    {"session_id": "9930b99fd96843f58edd65e49f56c8b9", "path": "/payments"}, 
    {"session_id": "72c04277ec21427e89a71b50d58f2e0d", "path": "/home"}, 
    {"session_id": "8ec2b63530634f839b5a106888145fb8", "path": "/details"}, 
    {"session_id": "425d08e4b32a491cbedff82a622e3a27", "path": "/support"}, 
    {"session_id": "aec5075b8f0c40538f40b3ad65ac6196", "path": "/upgrade"}, 
    {"session_id": "9930b99fd96843f58edd65e49f56c8b9", "path": "/payments"}, 
    {"session_id": "aec5075b8f0c40538f40b3ad65ac6196", "path": "/details"}, 
    {"session_id": "72c04277ec21427e89a71b50d58f2e0d", "path": "/support"}, 
    {"session_id": "8ec2b63530634f839b5a106888145fb8", "path": "/payments"}, 
    {"session_id": "425d08e4b32a491cbedff82a622e3a27", "path": "/support"}, 
    {"session_id": "aec5075b8f0c40538f40b3ad65ac6196", "path": "/home"}, 
    {"session_id": "9930b99fd96843f58edd65e49f56c8b9", "path": "/support"}, 
    {"session_id": "cbd86924fdd84af885a63350a78f1c09", "path": "/upgrade"}
]
```
Output
```
[
    {"session_id": "aec5075b8f0c40538f40b3ad65ac6196", "count": 4},
    {"session_id": "72c04277ec21427e89a71b50d58f2e0d", "count": 3},
    {"session_id": "8ec2b63530634f839b5a106888145fb8", "count": 3},
    {"session_id": "cbd86924fdd84af885a63350a78f1c09", "count": 2},
    {"session_id": "9930b99fd96843f58edd65e49f56c8b9", "count": 2},
    {"session_id": "425d08e4b32a491cbedff82a622e3a27", "count": 1}
]
```
*/

const INPUT_ARR = [
  { session_id: 'aec5075b8f0c40538f40b3ad65ac6196', path: '/payments' },
  { session_id: 'aec5075b8f0c40538f40b3ad65ac6196', path: '/upgrade' },
  { session_id: '72c04277ec21427e89a71b50d58f2e0d', path: '/details' },
  { session_id: '8ec2b63530634f839b5a106888145fb8', path: '/payments' },
  { session_id: 'cbd86924fdd84af885a63350a78f1c09', path: '/details' },
  { session_id: '9930b99fd96843f58edd65e49f56c8b9', path: '/payments' },
  { session_id: '72c04277ec21427e89a71b50d58f2e0d', path: '/home' },
  { session_id: '8ec2b63530634f839b5a106888145fb8', path: '/details' },
  { session_id: '425d08e4b32a491cbedff82a622e3a27', path: '/support' },
  { session_id: 'aec5075b8f0c40538f40b3ad65ac6196', path: '/upgrade' },
  { session_id: '9930b99fd96843f58edd65e49f56c8b9', path: '/payments' },
  { session_id: 'aec5075b8f0c40538f40b3ad65ac6196', path: '/details' },
  { session_id: '72c04277ec21427e89a71b50d58f2e0d', path: '/support' },
  { session_id: '8ec2b63530634f839b5a106888145fb8', path: '/payments' },
  { session_id: '425d08e4b32a491cbedff82a622e3a27', path: '/support' },
  { session_id: 'aec5075b8f0c40538f40b3ad65ac6196', path: '/home' },
  { session_id: '9930b99fd96843f58edd65e49f56c8b9', path: '/support' },
  { session_id: 'cbd86924fdd84af885a63350a78f1c09', path: '/upgrade' },
];

type PathUsage = {
  lastPath: string;
  count: number;
};

type Sessions = {
  [key: string]: PathUsage;
};

const sessionsObj: Sessions = {};

// build the sessionsObj
INPUT_ARR.forEach((input) => {
  // I could have used the object deconstructuring const { session_id, path } = input;
  // but for a better readability it's prefererable
  // to use input.session_id and input.path

  const sessionObjKeysArr = Object.keys(sessionsObj);

  if (sessionObjKeysArr.includes(input.session_id)) {
    // the input.session_id is already inside sessionsObj

    // check the path
    if (sessionsObj[input.session_id].lastPath !== input.path) {
      // increment count and update lastPath
      sessionsObj[input.session_id] = {
        lastPath: input.path,
        count: sessionsObj[input.session_id].count + 1,
      };
    }
  } else {
    // the input.session_id isn't inside the sessionsObj

    // create new entry and initialize count & lastPath
    sessionsObj[input.session_id] = {
      lastPath: input.path,
      count: 1,
    };
  }
});

// construct the output array
const outputArr = Object.entries(sessionsObj).map((sessionsObjEntry) => {
  const [session_id, { count }] = sessionsObjEntry;
  return {
    session_id,
    count,
  };
});

// sort the output array in descending order
outputArr.sort((a, b) => {
  return b.count - a.count;
});

console.log(outputArr);