Welcome! This lesson involves an engaging task that combines basic operations with array manipulation in PHP. We will be implementing a "Move Until Obstacle" game using an integer array. Visualize yourself as a game developer, and get ready to dive into the exciting world of problem-solving using PHP!
In the "Move Until Obstacle" game, the player begins at the start of a linear array of integers. The number at each position indicates how many steps a player has to move to the right. An obstacle number is one upon which the player cannot land. The goal is to move as far to the right as possible until either an obstacle stops the player or the player reaches the end of the array.
Your function, function solution($numbers, $obstacle), should tally and return the number of moves needed to reach the end of the array without encountering an obstacle. If the player encounters an obstacle, the function should return the index at which this obstacle lies.
For example, if the function receives the input: $numbers = [2, 3, 3, 4, 2, 4] and $obstacle = 4, it should return 5. This is because the player starts at the 0th index, takes 2 steps as indicated by the number at the 0th index (landing on the 2nd index), and then takes 3 more steps as indicated by the number at the 2nd index to land on the 5th index, which is the obstacle 4.
If the function receives the following input: $numbers = [4, 1, 2, 2, 4, 2, 2] and $obstacle = 2, the output should be 2. The player starts at the 0th index, takes 4 steps, lands on the 4th index, then takes 4 more steps, which brings the player outside the array, so the total number of steps the player takes is 2.
Our first step is to ensure we have variables to track the player, i.e., their current position and the moves they've taken so far. We'll name them $position and $moves, initializing both to 0:
php1<?php 2 3function solution($numbers, $obstacle) { 4 $position = 0; 5 $moves = 0;
Next, we'll use a while loop to iterate over the array. It continues as long as $position is less than the count of $numbers, which we obtain using count($numbers):
php1<?php 2 3function solution($numbers, $obstacle) { 4 $position = 0; 5 $moves = 0; 6 $length = count($numbers); 7 while ($position < $length) {
During each iteration, we need to check whether the player has encountered an obstacle. If so, we should return the $position at which this obstacle is located:
php1<?php 2 3function solution($numbers, $obstacle) { 4 $position = 0; 5 $moves = 0; 6 $length = count($numbers); 7 while ($position < $length) { 8 if ($numbers[$position] == $obstacle) { 9 return $position; 10 }
If the current number is not an obstacle, the player proceeds. The number of steps taken corresponds to the value at the current $position. We add this to $position and increment $moves:
php1<?php 2 3function solution($numbers, $obstacle) { 4 $position = 0; 5 $moves = 0; 6 $length = count($numbers); 7 while ($position < $length) { 8 if ($numbers[$position] == $obstacle) { 9 return $position; 10 } 11 $moves++; 12 $position += $numbers[$position]; 13 }
Once the loop ends, the player either has reached the end of the array or has encountered an obstacle. If the player managed to navigate the entirety of the array without encountering an obstacle, we want to return the total number of $moves:
The complete function looks like this:
php1<?php 2 3function solution($numbers, $obstacle) { 4 $position = 0; 5 $moves = 0; 6 $length = count($numbers); 7 8 while ($position < $length) { 9 // Check for obstacle at the current position 10 if ($numbers[$position] == $obstacle) { 11 return $position; // Return the index of the obstacle 12 } 13 // Increment moves and update position 14 $moves++; 15 $position += $numbers[$position]; // Move to the next position 16 } 17 18 // If loop ends without obstacles, return total moves taken 19 return $moves; 20} 21 22// Example usage 23echo solution([2, 3, 3, 4, 2, 4], 4); // Outputs: 5
Congratulations on successfully implementing the "Move Until Obstacle" game using PHP! You've navigated the challenges of this task by applying basic array manipulation concepts and operations with numbers in PHP. Celebrate your achievements, but don't stop there! Up next, we have practice sessions filled with similar exercises to reinforce your understanding and skills. So, gear up and let's keep moving!