Add task4 in php

Author: Holger Lösken

README.md

@@ -36,7 +36,32 @@ Write a `calculate` function that accepts an input and returns the result of the
 * Return 0 (integer) when nothing is entered
 * Return the numeric value when no operand is given, like `1 2 3.5` return `3.5`
 
+### Task 4
+
+Given you have an array of numbers, you move inside the array by the value of the current element.
+Write a function `jump_out_of_array` that outputs
+
+* the amount of jumps until you jump out of the array
+* `-1` when you reach the end of the array but do not jump out
+
+** Requirements:**
+* Array size is indefinite
+* Array elements are integers, positive and negative
+
+**Example:**
+
+Given an array of `A[2, 3, -1, 1, 6, 4]`.
+
+![](./docs/t4/task4.png)
+
+* Jump 1: A[0] + 2 = A[2]
+* Jump 2: A[2] + (-1) = A[1]
+* Jump 3: A[1] + 3 = A[4]
+* Jump 4: A[4] + 6 = out of range
+
+So the result is `4`, you need 4 jumps to jump out of the array.
+
 ## Contribute
 
 Feel free to contribute. Use the issue list to propose new tasks or open PRs. Just provide proper tests 
-and description and requirements for the tasks.
+and description and requirements for the tasks.

docs/t4/task4.png

@@ -1,6 +1,6 @@
 {
     "name": "codedge/coding-challenges",
-    "author": "Holger Lösken <[email protected]>",
+    "description": "",
     "require": {
         "php": "^8.0",
         "phpunit/phpunit": "^9.5"
@@ -9,7 +9,8 @@
         "files": [
             "t1/s1.php",
             "t2/s1.php",
-            "t3/s1.php"
+            "t3/s1.php",
+            "t4/s1.php"
         ],
         "psr-4": {
             "Tests\\": "tests/"

src/php/composer.json

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+function jump_out_of_array(array $a): int {
+    $sum = 0;
+    $jumps = 1;
+
+    // If first entry in array is negative, then the first jump is out of the array
+    if($a[0] < 0) {
+        return $jumps;
+    }
+
+    for ($i=0; $i<= count($a); $i++) {
+        $p = $a[$sum];
+        $sum = $sum + $p;
+
+        // Handle jumps out of array at the beginning of the array
+        if($sum < 0) {
+            return $jumps;
+        }
+
+        $jumps++;
+
+        // Handle jumps out of array at the end of the array
+        if (($sum + $p) > count($a)
+        ) {
+            return $jumps;
+        }
+
+        if(($i + 1) === count($a)) {
+            return -1;
+        }
+    }
+}

src/php/t4/s1.php

@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests;
+
+use PHPUnit\Framework\TestCase;
+
+final class T4Test extends TestCase
+{
+    public function testCanCheckJumpAtEndOfArray(): void
+    {
+        $this->assertSame(4, jump_out_of_array([2, 3, -1, 1, 6, 4]));
+    }
+
+    public function testCanCheckJumpAtBeginningOfArray(): void
+    {
+        $this->assertSame(1, jump_out_of_array([-1, 3, -1, 1, 6, 4]));
+    }
+
+    public function testCannotJumpOutOfArray(): void
+    {
+        $this->assertSame(-1, jump_out_of_array([1, 2, 1, 1, 1, 0]));
+    }
+}