fibo

Author: shakty

Diff for: Part_1_Basics/5_final_exercise.js

@@ -2,7 +2,8 @@
 // Welcome to the 3nd exercise sheet of Programming Fundamentals in JavaScript!
 ///////////////////////////////////////////////////////////////////////////////
 
-// Here we try to put things together
+// Here we try to put things together and we learn about a new thing:
+// recursion.
 
 // EXERCISE 1. Fibonacci.
 /////////////////////////
@@ -12,59 +13,48 @@
 // You can learn more here: https://en.wikipedia.org/wiki/Fibonacci_number
 
 // a. Implement a function that computes the fibonacci number for
-//  any input number.
-// For instance, if input is 10, the result is 55.
-
-function fibonacci(n) {
-    let fibo = [ 0, 1 ];
-    if (n < 2) return fibo[n];
-    for (let i=2; i <= n; i++) {
-        fibo[i] = fibo[i-1] + fibo[i-2];
-    }
-    return fibo[n];
-}
+// any input number. For instance, if input is 10, the result is 55.
+// Motivational Hint: This exercise is often asked at job interviews.
 
-fibonacci(10);
 
 // EXERCISE 2. Bonus. Recursive Fibonacci.
-
-// Recursion is the
-
-
-function fibonacciRecursive(n, counter) {
-    counter = counter || 0;
-    if (n > 1) fibo = fibonacciRecursive(n-1, n);
-    else fibo = n;
-    return fibo + counter;
+//////////////////////////////////////////
+
+// Recursion is a computer programming technique in which a function invokes
+// itslef inside its body. It's like playing with fire. It can be luring and
+// and elegant (specially if you work in a circus), but also very dangerous.
+// Your code could get stuck in an infinite loop of function calls which
+// ultimately will crash your program.
+
+// Here is an example of simple, but not so useful, recursive function
+// that counts until 5 and then returns
+
+function recursive(number = 5, stopCondition = 0) {
+    // Stopping-rule.
+    if (stopCondition === number) return stopCondition;
+    console.log('Counting...' + (stopCondition+1));
+    // Self-invocation with increment of the stopping condition.
+    return recursive(number, ++stopCondition);
 }
+resultOfRecursion = recursive(5);
+console.log(resultOfRecursion);
 
-fiboArray = [0, 1];
-function fibonacciRecursive(n) {
-    if (n > 2) {
-        fiboArray[n] = fibonacciRecursive(n-1);
-        fiboArray[n+1] = fibonacciRecursive(n) +
-        fibonacciRecursive(n-1);
-    }
-}
+// Cool! But what happens if you change ++stopCondition into stopCondition++?
+// You can try it, but make sure you save all your open files, because
+// you will get stuck in an infinite loop.
+// Small changes can cause big problems.
 
-fibonacciRecursive(10);
+// Now write the fibonacci recursive function.
+// Hint: it takes just 2 lines (but you could make it one).
 
-counter = 0;
-myInterval = setInterval(function() {
-    console.log(new Date());
-    if (++counter > 10) clearInterval(myInterval);
-}, 2000);
 
 
-// FUN EXERCISE
-
+// FUN EXERCISE!
+////////////////
 // You have done everything! You are a Jenius (shorthand for JavaScript Genius)!
 // Why don't you relax and have some fun programming a JS robot?
 // Check out: https://lab.reaal.me/jsrobot/
 
 
-
-
-
 // Great work! You finish the third exercise sheet!
 // Stop patting yourself, enough.

Diff for: Part_1_Basics/solutions/5_final_exercise.js

@@ -0,0 +1,79 @@
+////////////////////////////////////////////////////////////////////////////////
+// Welcome to the 3nd exercise sheet of Programming Fundamentals in JavaScript!
+///////////////////////////////////////////////////////////////////////////////
+
+// Here we try to put things together
+
+// EXERCISE 1. Fibonacci.
+/////////////////////////
+
+// The Fibonacci sequence is such that each number is the sum of
+// the two preceding ones in the sequence, starting from 0 and 1.
+// You can learn more here: https://en.wikipedia.org/wiki/Fibonacci_number
+
+// a. Implement a function that computes the fibonacci number for
+// any input number. For instance, if input is 10, the result is 55.
+// Motivational Hint: This exercise is often asked at job interviews.
+
+function fibonacci(n) {
+    let fibo = [ 0, 1 ];
+    if (n < 2) return fibo[n];
+    for (let i=2; i <= n; i++) {
+        fibo[i] = fibo[i-1] + fibo[i-2];
+    }
+    return fibo[n];
+}
+
+fibonacci(10);
+
+// EXERCISE 2. Bonus. Recursive Fibonacci.
+//////////////////////////////////////////
+
+// Recursion is a computer programming technique in which a function invokes
+// itslef inside its body. It's like playing with fire. It can be luring and
+// and elegant (specially if you work in a circus), but also very dangerous.
+// Your code could get stuck in an infinite loop of function calls which
+// ultimately will crash your program.
+
+// Here is an example of simple, but not so useful, recursive function
+// that counts until 5 and then returns
+
+function recursive(number = 5, stopCondition = 0) {
+    // Stopping-rule.
+    if (stopCondition === number) return stopCondition;
+    console.log('Counting...' + (stopCondition+1));
+    // Self-invocation with increment of the stopping condition.
+    return recursive(number, ++stopCondition);
+}
+resultOfRecursion = recursive(5);
+console.log(resultOfRecursion);
+
+// Cool! But what happens if you change ++stopCondition into stopCondition++?
+// You can try it, but make sure you save all your open files, because
+// you will get stuck in an infinite loop.
+// Small changes can cause big problems.
+
+// Now write the fibonacci recursive function.
+// Hint: it takes just 2 lines (but you could make it one).
+
+function fiboRec(n) {
+    if (n < 2) return n;
+    return fiboRec(n-1) + fiboRec(n-2);
+}
+fiboRec(10);
+
+// One-liner.
+function fiboRec1(n) {
+    return n < 2 ?  n : fiboRec1(n-1) + fiboRec1(n-2);
+}
+fiboRec1(10);
+
+// FUN EXERCISE!
+////////////////
+// You have done everything! You are a Jenius (shorthand for JavaScript Genius)!
+// Why don't you relax and have some fun programming a JS robot?
+// Check out: https://lab.reaal.me/jsrobot/
+
+
+// Great work! You finish the third exercise sheet!
+// Stop patting yourself, enough.