Merge pull request #3517 from gabrielmoris/06-php

#6 - php

Roadmap/06 - RECURSIVIDAD/php/gabrielmoris.php

@@ -0,0 +1,86 @@
+<?php
+/*
+ * EXERCISE:
+ * Understand the concept of recursion by creating a recursive function that
+ * prints numbers from 100 to 0.
+ */
+
+$num = 0;
+
+function recursive_print(&$num)
+{
+    do {
+        echo $num . "\n";
+        $num++;
+    } while ($num < 101);
+}
+
+recursive_print($num);
+
+/* EXTRA DIFFICULTY (optional):
+ * Use the concept of recursion to:
+ * - Calculate the factorial of a specific number (the function receives that number).
+ * - Calculate the value of a specific element (according to its position) in the
+ *   Fibonacci sequence (the function receives the position).
+ */
+
+
+
+function factorial($num)
+{
+    if ($num < 0) {
+        return "Error: Factorial of a negative number doesn't exist.";
+    } elseif ($num == 0 || $num == 1) {
+        return 1;
+    } else {
+        return (int)$num * (int)factorial($num - 1); // In this way I am specifying the return type as (int)
+    }
+}
+
+
+$num = 7;
+$fac = factorial($num);
+echo "Factorial of " . $num . " is " . $fac . "\n";
+
+$memo = [];
+
+function fibonacci($pos, &$memo)
+{
+    if ($pos <= 2) {
+        return 1;
+    }
+
+    if (!isset($memo[$pos])) {
+        $memo[$pos] = fibonacci($pos - 1, $memo) + fibonacci($pos - 2, $memo);
+    }
+
+    return $memo[$pos];
+}
+
+$fib = fibonacci($num, $memo);
+echo "Fibonacci in possition " . $num . " is " . $fib . "\n";
+
+
+function get_fibo_pos($num)
+{
+
+    $memo = [];
+    $pos = 0;
+    $fib_res = fibonacci($pos, $memo);
+
+    do {
+        $pos++;
+        $fib_res = fibonacci($pos, $memo);
+    } while ($num > $fib_res);
+
+
+    if ($num != $fib_res) {
+        return "Error: This Number doesn't belong to fibonacci sequence.";
+    }
+
+    return $pos;
+}
+
+$fibo_num = 1346269;
+$posi = get_fibo_pos($fibo_num);
+echo "Fibonacci possition of number " . $fibo_num . " is " . $posi . "\n";