HackerRank Dictionaries and Maps Problem


Given n names and phone numbers, assemble a phone book that maps friends’ names to their respective phone numbers.
You will then be given an unknown number of names to query your phone book for.
For each name queried, print the associated entry from your phone book on a new line in the form name=phoneNumber; if an entry for the name  is not found, print Not found instead.

💡 Note: Your phone book should be a Dictionary/Map/HashMap data structure.

Input Format

The first line contains an integer, n, denoting the number of entries in the phone book.
Each of the n subsequent lines describes an entry in the form of space-separated values on a single line. The first value is a friend’s name, and the second value is a phone number.

After the n  lines of phone book entries, there are an unknown number of lines of queries. Each line (query) contains a name to look up, and you must continue reading lines until there is no more input.

Output Format

On a new line for each query, print Not found if the name has no corresponding entry in the phone book; otherwise, print the full name and number in the format name=phoneNumber.

Sample -

sam 99912222
tom 11122222
harry 12299933
Not found


💡 Let’s Understand flow and solution line by line first as per the problem statement –

  • As per the problem statement, the input format is given line by line.
  • To process our given input, we need to split input by ‘\n’, which means by a line.
  • In the problem, it is given that the first line is the number of entries that means ‘n’. So input[0] will be the total entries.
  • Now let’s create a map data structure to store phone entries. const contacts = new Map();
  • Numbers are given from the first line to n, so we will run a for loop from 1 to n.
  • Phone number and Name are given in space-separated, so split values by one space. [0] is the name and [1] is the phone number.
  • After the n lines of phone book entries, there are an unknown number of lines of queries.
  • Now, let’s run a loop from n to the length of input given. And check if query exists in the map then print ‘name=phoneNumber’ & if not found the print ‘not found.
function processData(input) {
    //Enter your code here
   const inputList = input.split('\n'); //split input by line-break 
    const totalEntries = Number(inputList[0]);
    const contacts =  new Map();
    for(let i = 1; i <= totalEntries; i++) {
        const phoneDetails = inputList[i].split(' ');
        contacts.set(phoneDetails[0], phoneDetails[1]);
    for(let j = totalEntries+1; j <= inputList.length - 1; j++) {
        const query = inputList[j];
        if(!contacts.has(query)) {
          console.log('Not found');
        } else {

_input = "";
process.stdin.on("data", function (input) {
    _input += input;

process.stdin.on("end", function () {

HackerRank Dictionaries and Maps Problem

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