Pairing Opposite Characters in String
Introduction
Hello and welcome to our exciting exploration of PHP string manipulation! Today's lesson is particularly interesting: you will learn how to access characters from a string following a distinctive pattern using PHP. Our presentation is both comprehensive and concise, allowing you to master the concept quickly. Let's get started!
Task Statement
Imagine this: You receive a string, from which you need to extract characters, but the sequence in which you select them diverges from the norm. You start with the first character, then select the last character, move to the second character, then choose the second-to-last character, and continue this pattern until there are no characters left. Quite a mind-bender, isn't it?
Here's what we mean:
You are required to craft a PHP function, solution($inputString), within a PHP script. This function takes $inputString as a parameter, a string of lowercase English alphabet letters ('a' to 'z'), with a length ranging between 1 to 100 characters. The function then returns a new string, fashioned from the input string, but with characters selected in the pattern we described above.
For example, if the $inputString is "abcdefg", the function should return "agbfced".
Solution Building: Step 1 - Initialization
Before we delve into the problem-solving aspect, let's arrange our result store. We initialize a variable, $result, as an empty string to stockpile the output.
Step 2 - Looping over the string
Upon initialization, we need to traverse the $inputString. PHP furnishes a for loop to iterate over the elements in a string efficiently.
Now, the question arises: What is the requisite number of iterations for our loop? Given that we select two characters per iteration — one from the beginning and one from the end — we need the loop to run for half of the string's length if the length is even or half the length plus one if it's odd to include the middle character.
We can realize this by employing intdiv(strlen($inputString), 2) + strlen($inputString) % 2. This ensures the loop iterates for half the length if it is even and half the length plus one if it's odd.
Here's our function thus far:
