What is the reason for the effectiveness of utilizing bracket notation in this scenario?

Question

What is the reason for the effectiveness of utilizing bracket notation in this scenario?

Currently delving into Javascript, I encountered a tricky challenge on Hackerrank that left me stumped. The task was to determine the number of pairs of socks in a given pile. After some searching, I stumbled upon a solution which utilized bracket notation with an empty object called socks. This approach returned both numbers and undefined values, leaving me puzzled. Why would this work? Socks was originally supposed to be empty.

function sockMerchant(n, arr) {
    // var sorted = arr.sort();

    let socks = {}
    let pairs = 0;
    for (let i=0; i < n; i++) {
        // console.log(socks[arr[i]])


        socks[arr[i]] = socks[arr[i]] + 1 || 1;


        if (socks[arr[i]] % 2 === 0) {
            pairs += 1
        }
    }
    return console.log(pairs)
}

sockMerchant(11, [10, 20, 20, 10, 10, 30, 50, 10, 20, 50, 50])

javascript

Answer 1

Answer №1

Let's dive into the breakdown of this code:

We initiate by calling

sockMerchant(11, [10, 20, 20, 10, 10, 30, 50, 10, 20, 50, 50])

n represents the number of steps
arr denotes the array

Great.

We establish default values as follows:

let socks = {} //<- mapping object for socks [sock_name, count]
let pairs = 0;

Next, we iterate from 0 to n and perform the following actions:

Increase the count of found socks in the collection

socks[arr[i]] = socks[arr[i]] + 1 || 1;

If the count is even -> increment the pairs count

Let's review some scenarios:

socks[10] = 1
pairs = 0
socks[20] = 1
pairs = 0
socks[20] = 2
pairs = 1
socks[10] = 2
pairs = 2
socks[10] = 3
pairs = 2
...

Using bracket notation on an object/map can both retrieve the value or set/create one

Lastly:
The console.log function always returns undefined.
Remember to use return pairs

function sockMerchant(n, arr) {
    // initialization
    let socks = {}
    let pairs = 0;
    for (let i=0; i < n; i++) {
        // increment sock 'arr[i]' count
        socks[arr[i]] = socks[arr[i]] + 1 || 1;

        // check for a pair
        if (socks[arr[i]] % 2 === 0) {
            pairs += 1
        }
    }

    return pairs
}

foundPairs = sockMerchant(11, [10, 20, 20, 10, 10, 30, 50, 10, 20, 50, 50])

// foundPairs = 4

https://i.sstatic.net/RKS0H.png

Answer 2

Let's dive into the breakdown of this code:

We initiate by calling

sockMerchant(11, [10, 20, 20, 10, 10, 30, 50, 10, 20, 50, 50])

n represents the number of steps
arr denotes the array

Great.

We establish default values as follows:

let socks = {} //<- mapping object for socks [sock_name, count]
let pairs = 0;

Next, we iterate from 0 to n and perform the following actions:

Increase the count of found socks in the collection

socks[arr[i]] = socks[arr[i]] + 1 || 1;

If the count is even -> increment the pairs count

Let's review some scenarios:

socks[10] = 1
pairs = 0
socks[20] = 1
pairs = 0
socks[20] = 2
pairs = 1
socks[10] = 2
pairs = 2
socks[10] = 3
pairs = 2
...

Using bracket notation on an object/map can both retrieve the value or set/create one

Lastly:
The console.log function always returns undefined.
Remember to use return pairs

function sockMerchant(n, arr) {
    // initialization
    let socks = {}
    let pairs = 0;
    for (let i=0; i < n; i++) {
        // increment sock 'arr[i]' count
        socks[arr[i]] = socks[arr[i]] + 1 || 1;

        // check for a pair
        if (socks[arr[i]] % 2 === 0) {
            pairs += 1
        }
    }

    return pairs
}

foundPairs = sockMerchant(11, [10, 20, 20, 10, 10, 30, 50, 10, 20, 50, 50])

// foundPairs = 4

https://i.sstatic.net/RKS0H.png

What is the reason for the effectiveness of utilizing bracket notation in this scenario?

Answer №1

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