PHP Exercises: Check whether the sequence of numbers 1, 2, 3 appears in a given array of integers somewhere

PHP Basic Algorithm: Exercise-34 with Solution

Write a PHP program to check whether the sequence of numbers 1, 2, 3 appears in a given array of integers somewhere.

Sample Solution:

PHP Code :

<?php
// Define a function that checks if the sequence 1, 2, 3 appears in an array
function test($nums)
{
    // Iterate through the array to find the sequence
    for ($i = 0; $i < sizeof($nums)-2; $i++)
    {
        // Check if the current, next, and next-next elements form the sequence 1, 2, 3
        if ($nums[$i] == 1 && $nums[$i + 1] == 2 && $nums[$i + 2] == 3)
            return true;
    }
    
    // If the sequence is not found, return false
    return false;
}

// Test the function with different arrays
var_dump(test(array(1,1,2,3,1)));
var_dump(test(array(1,1,2,4,1)));
var_dump(test(array(1,1,2,1,2,3)));
?>

Explanation:

• Function Definition:
• The test function takes an array of numbers $nums as input and checks if the sequence [1, 2, 3] appears anywhere in the array.
• Loop through Array:
• The for loop iterates from the start of the array up to the third-to-last element to ensure there are enough elements left to check for the sequence.
• sizeof($nums) - 2 ensures we don't go out of bounds when checking three consecutive elements.
• Check for Sequence:
• Inside the loop, the code checks if three consecutive elements form the sequence [1, 2, 3] by comparing:
• $nums[$i] == 1
• $nums[$i + 1] == 2
• $nums[$i + 2] == 3
• If the sequence is found, the function returns true.
• Return False if Sequence Not Found:
• If the loop completes without finding the sequence [1, 2, 3], the function returns false.

Output:

bool(true)
bool(false)
bool(true)

Visual Presentation:

Flowchart:

PHP Code Editor:

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