Categories
General

Passing Yearbooks Facebook

There are n students, numbered from 1 to n, each with their own yearbook. They would like to pass their yearbooks around and get them signed by other students.You’re given a list of n integers arr[1..n], which is guaranteed to be a permutation of 1..n (in other words, it includes the integers from 1 to n exactly once each, in some order). The meaning of this list is described below.Initially, each student is holding their own yearbook. The students will then repeat the following two steps each minute: Each student i will first sign the yearbook that they’re currently holding (which may either belong to themselves or to another student), and then they’ll pass it to student arr[i-1]. It’s possible that arr[i-1] = i for any given i, in which case student i will pass their yearbook back to themselves. Once a student has received their own yearbook back, they will hold on to it and no longer participate in the passing process.It’s guaranteed that, for any possible valid input, each student will eventually receive their own yearbook back and will never end up holding more than one yearbook at a time.You must compute a list of n integers output, whose element at i-1 is equal to the number of signatures that will be present in student i’s yearbook once they receive it back.

Signature

int[] findSignatureCounts(int[] arr)

Input

n is in the range [1, 100,000]. Each value arr[i] is in the range [1, n], and all values in arr[i] are distinct.

Output

Return a list of n integers output, as described above.

Example 1

  • Student 1 signs their own yearbook. Then they pass the book to the student at arr[0], which is Student 2.
  • Student 2 signs their own yearbook. Then they pass the book to the student at arr[1], which is Student 1.

n = 2 arr = [2, 1] output = [2, 2]Pass 1:

Pass 2:

  • Student 1 signs Student 2’s yearbook. Then they pass it to the student at arr[0], which is Student 2.
  • Student 2 signs Student 1’s yearbook. Then they pass it to the student at arr[1], which is Student 1.

Pass 3:

  • Both students now hold their own yearbook, so the process is complete.

Each student received 2 signatures.

Example 2

n = 2 arr = [1, 2] output = [1, 1]Pass 1:

  • Student 1 signs their own yearbook. Then they pass the book to the student at arr[0], which is themself, Student 1.
  • Student 2 signs their own yearbook. Then they pass the book to the student at arr[1], which is themself, Student 2.

Pass 2:

  • Both students now hold their own yearbook, so the process is complete.

function findSignatureCounts($arr) {
  foreach ($arr as $index => $studentNumber) {
   //   var_dump('Book for student '.$studentNumber);

    $bookedSigned[$studentNumber] = [$studentNumber];
  
    dfs($arr[$studentNumber - 1], $studentNumber, $index, $bookedSigned, $arr);
    
    $result[] = count($bookedSigned[$studentNumber] );
   
    
}

//var_dump('$result');
//var_dump($result);

  return $result;


  
}



function dfs($newStudentNumber, $studentNumber, $studentIndex, &$bookedSigned, $arr) {
    if(in_array($newStudentNumber, $bookedSigned[$studentNumber])){
        return;        
    }
    $bookedSigned[$studentNumber][] = $newStudentNumber;
     // var_dump( 'for student '.$studentNumber.' Book signed by');
    //  var_dump($bookedSigned[$studentNumber] );
    
    if(($studentNumber - 1) < 0) {
        return;        
    }



     dfs($arr[$newStudentNumber - 1], $studentNumber, $studentIndex, $bookedSigned, $arr);
}

Categories
General

Rotational Cipher Facebook

One simple way to encrypt a string is to “rotate” every alphanumeric character by a certain amount. Rotating a character means replacing it with another character that is a certain number of steps away in normal alphabetic or numerical order.For example, if the string “Zebra-493?” is rotated 3 places, the resulting string is “Cheud-726?”. Every alphabetic character is replaced with the character 3 letters higher (wrapping around from Z to A), and every numeric character replaced with the character 3 digits higher (wrapping around from 9 to 0). Note that the non-alphanumeric characters remain unchanged.Given a string and a rotation factor, return an encrypted string.

Signature

string rotationalCipher(string input, int rotationFactor)

Input

1 <= |input| <= 1,000,000 0 <= rotationFactor <= 1,000,000

Output

Return the result of rotating input a number of times equal to rotationFactor.

Example 1

input = Zebra-493? rotationFactor = 3 output = Cheud-726?

Example 2

input = abcdefghijklmNOPQRSTUVWXYZ0123456789 rotationFactor = 39 output = nopqrstuvwxyzABCDEFGHIJKLM9012345678

function rotationalCipher($input, $rotation_factor) {
  
            for($i=0; $i< 26;$i++) {
              $letter = chr(97 + $i);
              $alphabetMap[$letter] = $i;
          }   
   
        $newString = '';
        $input = str_split($input);
        foreach ($input as $item) {
            #Da
            //Sanity Check
            if(!ctype_alpha($item) && !is_numeric($item))
            {
                 $newString .= $item;
            }
            //if character
            if(ctype_alpha($item))
            {
                #item D;a
                $initialstateUpperCase = false; 
                if (ctype_upper($item)) {
                    $initialstateUpperCase = true; #D
                    $item = strtolower($item);  #d
                }
                
                $value = $alphabetMap[$item]; #3;0
                $newValue = $value + $rotation_factor; #5;2
                if($newValue > 26) {
                    $newValue = $newValue % 26;
                }
                $newCharacter = array_search($newValue, $alphabetMap); #f;c
                if($initialstateUpperCase === true)
                {
                    $newCharacter = strtoupper($newCharacter);    #F
                }
            
                $newString .= $newCharacter; #Fc
            }
            
            
            //if integer
            if(is_numeric($item))
            {
                $newValue = $item + $rotation_factor;
                if($newValue > 10) {
                    $newValue = $newValue % 10;
                }
                $newString .= $newValue;
            }
        }
            return $newString;            
  
  
}  

Categories
General

Contiguous Subarrays Facebook

You are given an array arr of N integers. For each index i, you are required to determine the number of contiguous subarrays that fulfill the following conditions:

  • The value at index i must be the maximum element in the contiguous subarrays, and
  • These contiguous subarrays must either start from or end on index i.

Signature int[] countSubarrays(int[] arr)Input

  • Array arr is a non-empty list of unique integers that range between 1 to 1,000,000,000
  • Size N is between 1 and 1,000,000

Output An array where each index i contains an integer denoting the maximum number of contiguous subarrays of arr[i]Example: arr = [3, 4, 1, 6, 2] output = [1, 3, 1, 5, 1]Explanation:

  • For index 0 – [3] is the only contiguous subarray that starts (or ends) with 3, and the maximum value in this subarray is 3.
  • For index 1 – [4], [3, 4], [4, 1]
  • For index 2 – [1]
  • For index 3 – [6], [6, 2], [1, 6], [4, 1, 6], [3, 4, 1, 6]
  • For index 4 – [2]

So, the answer for the above input is [1, 3, 1, 5, 1]

 function countSubarrays(array $arr){
        $result = array();
        
        #traverse the $arr
        
        foreach ($arr as $index => $value){
            # index 0 value 3 
            # index 1 value 4
            
            # index 3 value 6

            $totalCountSubArray = 1;
            
             # 0
                $countSubbarrayLeftToRight = 
                    leftToRightSlidingWindow($index, $arr, $value);
                    
                
             # 0
                $countSubbarrayRightToleft = 
                    rightToLeftSlidingWindow($index, $arr, $value);
                    
            #$result[1]; 
                $result[] = $totalCountSubArray + 
                    $countSubbarrayLeftToRight + 
                    $countSubbarrayRightToleft;
            
        }
        
        return $result;
    }
Categories
General

Pair Sums Facebook

Pair SumsGiven a list of n integers arr[0..(n-1)], determine the number of different pairs of elements within it which sum to k.If an integer appears in the list multiple times, each copy is considered to be different; that is, two pairs are considered different if one pair includes at least one array index which the other doesn’t, even if they include the same values.

Signature

int numberOfWays(int[] arr, int k)

Input

n is in the range [1, 100,000]. Each value arr[i] is in the range [1, 1,000,000,000]. k is in the range [1, 1,000,000,000].

Output

Return the number of different pairs of elements which sum to k.

Example 1

n = 5 k = 6 arr = [1, 2, 3, 4, 3] output = 2The valid pairs are 2+4 and 3+3.

Example 2

n = 5 k = 6 arr = [1, 5, 3, 3, 3] output = 4There’s one valid pair 1+5, and three different valid pairs 3+3 (the 3rd and 4th elements, 3rd and 5th elements, and 4th and 5th elements).


class Solution {
    
    public function __construct(){
        
    }
    
    public function numberOfWays(array $arr, int $k) : int {
        sort($arr); # [1,3,3,3,5]
        $sortedArr = $arr;
        

        
        $p1PrevValue = null;
        $p1Index = 0;
        $p2Index = count($sortedArr) - 1; #$p2Index 4
        $p2Value = $sortedArr[$p2Index]; #$p2Value 5
        $prevP1 = null;
        $countOfWays = 0;
        
        #traverse array
         #$p1Index 0
        #$p2Index 4

        
        while ($p1Index < $p2Index) {
            $p1Value = $sortedArr[$p1Index]; # 1;3,3
            $p2Value = $sortedArr[$p2Index]; # 3;3,3


            
            if($p1Value + $p2Value === $k) { 
                $countOfWays++; #1;2;3
                if($p1Value === $p1PrevValue) {
                    $countOfWays++; #4
                }
                $p1PrevValue = $p1Value; #1;3
                $p1Index++;# 1;2,3
            }
            
            if($p1Value + $p2Value > $k) {
                $p2Index--; #3
            }

            if($p1Value + $p2Value < $k) {
                $p1Index++;
            }
        }
    return $countOfWays;

    }
}

$solution = new Solution();
$k = 6;
$arr = [1,5,3,3,3];

$countOfWays = $solution->numberOfWays($arr, $k);

var_dump($countOfWays);
Categories
General

Phone Numbers

<?php

class Solution {

    private $hasmapExistingLetters;
    private $phoneKeyPad =
        array(
            1 => [],
            2 => ['a','b','c'],
            3 => ['d','e','f'],
            4 => ['g','h','i'],
            5 => ['j','k','l'],
            6 => ['m','n','o'],
            7 => ['p','q','r','s'],
            8 => ['t','u','v'],
            9 => ['w','x','y','z']
        );

    public function __construct(string $phonenumber){
        $this->hasmapExistingLetters = $this->buildHashmap($phonenumber);
        // var_dump($this->hasmapExistingLetters);
    }

    #364
    public function buildHashmap(string $phonenumber ) {
        $phonenumber = str_split($phonenumber);

        foreach ($phonenumber as $index => $singleDigit) {

            # singleDigit = 3 inex =0    
            $letters = $this->phoneKeyPad[$singleDigit];
            #letters =    ['d','e','f'],


            foreach ($letters as $letter){
                #hasmapExistingLetters['d'] = 0;   
                #hasmapExistingLetters['e'] = 0;   
                #hasmapExistingLetters['f'] = 0;   

                #hasmapExistingLetters['m'] = 1;   
                #hasmapExistingLetters['n'] = 1;   
                #hasmapExistingLetters['o'] = 1;   

                #hasmapExistingLetters['g'] = 2;   
                #hasmapExistingLetters['h'] = 2;   
                #hasmapExistingLetters['i'] = 2;   
                //var_dump($letter);
                $hasmapExistingLetters[$letter] = $index;
            }
        }

        // var_dump($hasmapExistingLetters);
        return $hasmapExistingLetters;
    }


    public function returnValidWords( array $validWordsInput) : array {

        foreach ($validWordsInput as $word) {
            #dog
            $validWord = true;
            //var_dump($wordToDissect);
            $len = strlen($word);
            for ($index=0; $index < $len; $index++) {
                # 0 => d
                # 1 => o
                # 2 => g
                $letter = $word[$index];

                if(!array_key_exists($letter, $this->hasmapExistingLetters)
                    && $this->hasmapExistingLetters[$letter] !== $index) {
                    $validWord = false;
                }
            }

            if($validWord === true)
                $resultValidWord[] = $word;
        }
        return $resultValidWord;
    }
}



$phoneNumber = '364';

$validWords =
    array('dog','fog','fish','water');

$solution = new Solution($phoneNumber);

$result = $solution->returnValidWords($validWords);

var_dump($result);




#build hasmap

#each validwords
#iterate through each letter
#check if ! exist in hasmap && index === validWord -> index
#return false
#return true

#resultValidword [] = theword

#return resultValidword;
#var_dump($phoneKeyPad);

Categories
General

Climbing stairs solution – similar to fibonnaci sequence

<?php


class Solution
{

    public static function climbingStairs(int $numberOfStairs)
    {
        $numberOfWays = 0;
        $numberOfWays = self::climbingStairsHelper($numberOfStairs);

        return $numberOfWays;
    }

    public static function climbingStairsHelper($numberOfStairs)
    {
        if ($numberOfStairs <= 0) {
            return 1;
        }
        return self::climbingStairsHelper($numberOfStairs - 1) + self::climbingStairsHelper($numberOfStairs - $numberOfStairs - 2);
    }

    public static function climbingStairsMemoization(int $numberOfStairs)
    {
        $numberOfWays = 0;
        $memo = array();
        for ($i = 0; $i < $numberOfStairs; $i++) {
            $memo[$i] = 0;
        }

        $memo[0] = 0;
        $memo[1] = 2;

        $numberOfWays = self::climbingStairsHelper($numberOfStairs, $memo);

        return $numberOfWays;
    }

    public static function climbingStairsHelperMemoization($numberOfStairs, &$memo)
    {

        if ($numberOfStairs <= 0) {
            return 1;
        }


        return self::climbingStairsHelper($numberOfStairs - 1) + self::climbingStairsHelper($numberOfStairs - $numberOfStairs - 2);
    }

}


//    var_dump(Solution::climbingStairs(2));

var_dump(Solution::climbingStairsMemoization(5));
Categories
General

Longest Substring Without Repeating Characters – Sliding Window

class Solution {
/**
 * @param String $s
 * @return Integer
 */
function lengthOfLongestSubstring($s) {
    $len = strlen($s);
    $max = 0;
    $tempMax = 0;
    $freq = array();

    #loop through array
    for($i = 0; $i < $len; $i++){


        #if IN character in freq array
        if(array_key_exists($s[$i], $freq)) {
            var_dump( $s[$i]);
            $max = max($max, $tempMax);
            $tempMax = 0;
            $this->resetFreq($freq);
        }
        else {
            #if not in freq array
            $freq[$s[$i]] = 1;
            $tempMax +=1 ;
        }

   }
    return $max;
}
public function resetFreq(array $freq) : array {

    return array();
}
}

Categories
General

Why Laravel valet on windows + VPN is not working ?

I am a mac user but I had to help some members of my team to get laravel running on their professional windows laptop running VPN

Solution found was to go to the following file

#1 – c:\Windows\System32\Drivers\etc\hosts

#2 – comment all lines with 127.0.0.1

#3 – add one line with the 127.0.0.1 and the url of the laravel valet app that you desire to get running

127.0.0.1. yourlaravel.test

Categories
General

How to resolve dyld: Library not loaded: /usr/local/opt/openldap/lib/libldap-2.5.0.dylib ?

Here are the following 2 commands to resolve issue

brew tap shivammathur/php
brew install shivammathur/php/[email protected]

Categories
General

What are Long and Short Polling in AWS SQS ?

Find below an amazing article about AWS SQS

https://laravel-news.com/amazon-sqs-tips?utm_medium=email&utm_campaign=You%20can%20now%20generate%20test%20files%20with%20Laravel%20make%20commands%20-%20382&utm_content=You%20can%20now%20generate%20test%20files%20with%20Laravel%20make%20commands%20-%20382+CID_d9fd547e177fba8f9a066975d2d06163&utm_source=email%20marketing&utm_term=Things%20I%20Didnt%20Know%20About%20SQS

Long and Short Polling

SQS’s API is all HTTP based. This means that when our queue workers poll SQS for a new job, it’s making an HTTP request to the SQS API.

By default, this does “short polling” – if no job is available when the HTTP request is made, SQS immediately returns an empty response.

Long polling allows you to keep an HTTP request open for a certain amount of time. While the HTTP request is open, SQS may send a job to the queue worker at any time.

Laravel doesn’t do any long polling, but there is something important to know here.

If you use the SQS queue driver, you may see that some jobs take a while to get processed – as if the queue worker can’t find a new job. This is related to how SQS is scaled within AWS.

Here’s the relevant thing to know, from the SQS docs:

With short polling, the ReceiveMessage request queries only a subset of the servers (based on a weighted random distribution) to find messages that are available to include in the response. Amazon SQS sends the response right away, even if the query found no messages.

With long polling, the ReceiveMessage request queries all of the servers for messages. Amazon SQS sends a response after it collects at least one available message, up to the maximum number of messages specified in the request. Amazon SQS sends an empty response only if the polling wait time expires.

It turns out that with long polling, we’re likely to get jobs more quickly as it polls all of the SQS servers that may contain our jobs!

However, Laravel doesn’t support long-polling out of the box. Luckily, we can do something about that. There’s a little note in the bottom of the docs linked above:

Short polling occurs when the WaitTimeSeconds parameter of a ReceiveMessage request is set to 0 in one of two ways:

  • The ReceiveMessage call sets WaitTimeSeconds to 0.
  • The ReceiveMessage call doesn’t set WaitTimeSeconds, but the queue attribute ReceiveMessageWaitTimeSeconds is set to 0.

https://laravel-news.com/amazon-sqs-tips?utm_medium=email&utm_campaign=You%20can%20now%20generate%20test%20files%20with%20Laravel%20make%20commands%20-%20382&utm_content=You%20can%20now%20generate%20test%20files%20with%20Laravel%20make%20commands%20-%20382+CID_d9fd547e177fba8f9a066975d2d06163&utm_source=email%20marketing&utm_term=Things%20I%20Didnt%20Know%20About%20SQS