Deciphering Uniqueness and Anagram Mysteries with PHP Arrays

Lesson Introduction

Welcome to our focused exploration of PHP's array functions and their powerful applications in algorithmic challenges. In this lesson, " Deciphering Uniqueness and Anagram Mysteries with PHP Arrays," we'll delve into how these functions can be harnessed to efficiently tackle problems commonly seen in technical interviews.

Problem 1: Unique Echo

Imagine: you’re presented with an extensive list of words, with the task to pinpoint the final word that stands alone — the last non-repeating word. This mirrors the challenge of sorting through a database of unique identifiers to identify a distinct one near the end.

Problem 1: Naive Approach

O(n^2)

Problem 1: Efficient Approach

O(n)

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PHP

$wordCounts = [];

PHP

foreach ($words as $word) {
    if (isset($wordCounts[$word])) {
        $wordCounts[$word]++;
    } else {
        $wordCounts[$word] = 1;
    }
}

PHP

$lastUniqueWord = "";
for ($i = count($words) - 1; $i >= 0; $i--) {
    if ($wordCounts[$words[$i]] == 1) {
        $lastUniqueWord = $words[$i];
        break;
    }
}

$lastUniqueWord = "";
for ($i = count($words) - 1; $i >= 0; $i--) {
    if ($wordCounts[$words[$i]] == 1) {
        $lastUniqueWord = $words[$i];
        break;
    }
}

PHP

return $lastUniqueWord;

return $lastUniqueWord;

PHP

<?php
function findLastUniqueWord($words) {
    // Step 1: Initialize an associative array for word counts
    $wordCounts = [];

    // Step 2: Count each word's occurrences as you traverse the list
    foreach ($words as $word) {
        if (isset($wordCounts[$word])) {
            $wordCounts[$word]++;
        } else {
            $wordCounts[$word] = 1;
        }
    }

    // Step 3: Identify the last unique word by traversing the array from the end
    $lastUniqueWord = "";
    for ($i = count($words) - 1; $i >= 0; $i--) {
        if ($wordCounts[$words[$i]] == 1) {
            $lastUniqueWord = $words[$i];
            break;
        }
    }

    // Step 4: Return the unique word
    return $lastUniqueWord;
}

// Example usage
$words = ["apple", "banana", "apple", "orange", "banana", "kiwi"];
echo findLastUniqueWord($words); // Output: kiwi
?>

<?php
function findLastUniqueWord($words) {
    // Step 1: Initialize an associative array for word counts
    $wordCounts = [];

    // Step 2: Count each word's occurrences as you traverse the list
    foreach ($words as $word) {
        if (isset($wordCounts[$word])) {
            $wordCounts[$word]++;
        } else {
            $wordCounts[$word] = 1;
        }
    }

    // Step 3: Identify the last unique word by traversing the array from the end
    $lastUniqueWord = "";
    for ($i = count($words) - 1; $i >= 0; $i--) {
        if ($wordCounts[$words[$i]] == 1) {
            $lastUniqueWord = $words[$i];
            break;
        }
    }

    // Step 4: Return the unique word
    return $lastUniqueWord;
}

// Example usage
$words = ["apple", "banana", "apple", "orange", "banana", "kiwi"];
echo findLastUniqueWord($words); // Output: kiwi
?>

PHP

$lastUniqueWord = "";
for ($i = count($words) - 1; $i >= 0; $i--) {
    if ($wordCounts[$words[$i]] == 1) {
        $lastUniqueWord = $words[$i];
        break;
    }
}

PHP

return $lastUniqueWord;

PHP

<?php
function findLastUniqueWord($words) {
    // Step 1: Initialize an associative array for word counts
    $wordCounts = [];

    // Step 2: Count each word's occurrences as you traverse the list
    foreach ($words as $word) {
        if (isset($wordCounts[$word])) {
            $wordCounts[$word]++;
        } else {
            $wordCounts[$word] = 1;
        }
    }

    // Step 3: Identify the last unique word by traversing the array from the end
    $lastUniqueWord = "";
    for ($i = count($words) - 1; $i >= 0; $i--) {
        if ($wordCounts[$words[$i]] == 1) {
            $lastUniqueWord = $words[$i];
            break;
        }
    }

    // Step 4: Return the unique word
    return $lastUniqueWord;
}

// Example usage
$words = ["apple", "banana", "apple", "orange", "banana", "kiwi"];
echo findLastUniqueWord($words); // Output: kiwi
?>

function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

$sortedWordsInArray2 = [];
foreach ($array2 as $word) {
    $sortedWordsInArray2[sortCharacters($word)] = true;
}

$result = [];
foreach ($array1 as $word) {
    $sortedWord = sortCharacters($word);
    if (isset($sortedWordsInArray2[$sortedWord])) {
        $result[] = $word;
    }
}

<?php
function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

function findAnagrams($array1, $array2) {
    // Step 2: Store signatures from array2 in an associative array for quick comparison
    $sortedWordsInArray2 = [];
    foreach ($array2 as $word) {
        $sortedWordsInArray2[sortCharacters($word)] = true;
    }

    // Step 3: Find anagrams by comparing each word's signature in array1 with stored signatures
    $result = [];
    foreach ($array1 as $word) {
        $sortedWord = sortCharacters($word);
        if (isset($sortedWordsInArray2[$sortedWord])) {
            $result[] = $word;
        }
    }

    // Step 4: Return the list of anagrams
    return $result;
}

// Example usage
$array1 = ["listen", "silent", "enlist", "google"];
$array2 = ["inlets", "banana", "google"];

print_r(findAnagrams($array1, $array2)); // Output: Array ( [0] => listen [1] => silent [2] => enlist [3] => google )
?>

PHP

function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

PHP

$sortedWordsInArray2 = [];
foreach ($array2 as $word) {
    $sortedWordsInArray2[sortCharacters($word)] = true;
}

$sortedWordsInArray2 = [];
foreach ($array2 as $word) {
    $sortedWordsInArray2[sortCharacters($word)] = true;
}

PHP

$result = [];
foreach ($array1 as $word) {
    $sortedWord = sortCharacters($word);
    if (isset($sortedWordsInArray2[$sortedWord])) {
        $result[] = $word;
    }
}

$result = [];
foreach ($array1 as $word) {
    $sortedWord = sortCharacters($word);
    if (isset($sortedWordsInArray2[$sortedWord])) {
        $result[] = $word;
    }
}

PHP

return $result;

PHP

<?php
function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

function findAnagrams($array1, $array2) {
    // Step 2: Store signatures from array2 in an associative array for quick comparison
    $sortedWordsInArray2 = [];
    foreach ($array2 as $word) {
        $sortedWordsInArray2[sortCharacters($word)] = true;
    }

    // Step 3: Find anagrams by comparing each word's signature in array1 with stored signatures
    $result = [];
    foreach ($array1 as $word) {
        $sortedWord = sortCharacters($word);
        if (isset($sortedWordsInArray2[$sortedWord])) {
            $result[] = $word;
        }
    }

    // Step 4: Return the list of anagrams
    return $result;
}

// Example usage
$array1 = ["listen", "silent", "enlist", "google"];
$array2 = ["inlets", "banana", "google"];

print_r(findAnagrams($array1, $array2)); // Output: Array ( [0] => listen [1] => silent [2] => enlist [3] => google )
?>

<?php
function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

function findAnagrams($array1, $array2) {
    // Step 2: Store signatures from array2 in an associative array for quick comparison
    $sortedWordsInArray2 = [];
    foreach ($array2 as $word) {
        $sortedWordsInArray2[sortCharacters($word)] = true;
    }

    // Step 3: Find anagrams by comparing each word's signature in array1 with stored signatures
    $result = [];
    foreach ($array1 as $word) {
        $sortedWord = sortCharacters($word);
        if (isset($sortedWordsInArray2[$sortedWord])) {
            $result[] = $word;
        }
    }

    // Step 4: Return the list of anagrams
    return $result;
}

// Example usage
$array1 = ["listen", "silent", "enlist", "google"];
$array2 = ["inlets", "banana", "google"];

print_r(findAnagrams($array1, $array2)); // Output: Array ( [0] => listen [1] => silent [2] => enlist [3] => google )
?>

PHP

function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

PHP

$sortedWordsInArray2 = [];
foreach ($array2 as $word) {
    $sortedWordsInArray2[sortCharacters($word)] = true;
}

PHP

$result = [];
foreach ($array1 as $word) {
    $sortedWord = sortCharacters($word);
    if (isset($sortedWordsInArray2[$sortedWord])) {
        $result[] = $word;
    }
}

PHP

return $result;

PHP

<?php
function sortCharacters($input) {
    $characters = str_split($input);
    sort($characters);
    return implode('', $characters);
}

function findAnagrams($array1, $array2) {
    // Step 2: Store signatures from array2 in an associative array for quick comparison
    $sortedWordsInArray2 = [];
    foreach ($array2 as $word) {
        $sortedWordsInArray2[sortCharacters($word)] = true;
    }

    // Step 3: Find anagrams by comparing each word's signature in array1 with stored signatures
    $result = [];
    foreach ($array1 as $word) {
        $sortedWord = sortCharacters($word);
        if (isset($sortedWordsInArray2[$sortedWord])) {
            $result[] = $word;
        }
    }

    // Step 4: Return the list of anagrams
    return $result;
}

// Example usage
$array1 = ["listen", "silent", "enlist", "google"];
$array2 = ["inlets", "banana", "google"];

print_r(findAnagrams($array1, $array2)); // Output: Array ( [0] => listen [1] => silent [2] => enlist [3] => google )
?>

Lesson Introduction

Problem 1: Unique Echo

Problem 1: Naive Approach

Problem 1: Efficient Approach

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Problem 2: Anagram Matcher

Problem 2: Efficient Approach

Lesson Summary