Added fibonacci sequence as well as fibonacci nth, renamed functions accordingly (trekhleb#36)

Author: ohepworthbell

src/algorithms/math/fibonacci/__test__/fibonacci.test.js

@@ -2,14 +2,13 @@ import fibonacci from '../fibonacci';
 
 describe('fibonacci', () => {
   it('should calculate fibonacci correctly', () => {
-    expect(fibonacci(1)).toBe(1);
-    expect(fibonacci(2)).toBe(1);
-    expect(fibonacci(3)).toBe(2);
-    expect(fibonacci(4)).toBe(3);
-    expect(fibonacci(5)).toBe(5);
-    expect(fibonacci(6)).toBe(8);
-    expect(fibonacci(7)).toBe(13);
-    expect(fibonacci(8)).toBe(21);
-    expect(fibonacci(20)).toBe(6765);
+    expect(fibonacci(1)).toEqual([1]);
+    expect(fibonacci(2)).toEqual([1, 1]);
+    expect(fibonacci(3)).toEqual([1, 1, 2]);
+    expect(fibonacci(4)).toEqual([1, 1, 2, 3]);
+    expect(fibonacci(5)).toEqual([1, 1, 2, 3, 5]);
+    expect(fibonacci(6)).toEqual([1, 1, 2, 3, 5, 8]);
+    expect(fibonacci(7)).toEqual([1, 1, 2, 3, 5, 8, 13]);
+    expect(fibonacci(8)).toEqual([1, 1, 2, 3, 5, 8, 13, 21]);
   });
 });

src/algorithms/math/fibonacci/__test__/fibonacciNth.test.js

@@ -0,0 +1,15 @@
+import fibonacciNth from '../fibonacciNth';
+
+describe('fibonacciNth', () => {
+  it('should calculate fibonacci correctly', () => {
+    expect(fibonacciNth(1)).toBe(1);
+    expect(fibonacciNth(2)).toBe(1);
+    expect(fibonacciNth(3)).toBe(2);
+    expect(fibonacciNth(4)).toBe(3);
+    expect(fibonacciNth(5)).toBe(5);
+    expect(fibonacciNth(6)).toBe(8);
+    expect(fibonacciNth(7)).toBe(13);
+    expect(fibonacciNth(8)).toBe(21);
+    expect(fibonacciNth(20)).toBe(6765);
+  });
+});

src/algorithms/math/fibonacci/fibonacci.js

@@ -1,26 +1,24 @@
-// Calculate fibonacci number at specific position using Dynamic Programming approach.
-export default function fibonacci(numberPosition) {
-  if (numberPosition === 1) {
-    return 1;
-  }
+// Return a fibonacci sequence as an array
+export default function fibonacci(n) {
+  const fibSequence = [1];
+
+  let currentValue = 1;
+  let previousValue = 0;
 
-  let iterationsCounter = numberPosition - 1;
+  if (n === 1) {
+    return fibSequence;
+  }
 
-  // Calculated fibonacci number.
-  let fib = null;
-  // Previous fibonacci number.
-  let fibPrev = 1;
-  // Before previous fibonacci number.
-  let fibPrevPrev = 0;
+  let iterationsCounter = n - 1;
 
   while (iterationsCounter) {
-    // Calculate current value using two previous ones.
-    fib = fibPrev + fibPrevPrev;
-    // Shift previous values.
-    fibPrevPrev = fibPrev;
-    fibPrev = fib;
+    currentValue += previousValue;
+    previousValue = (currentValue - previousValue);
+
+    fibSequence.push(currentValue);
+
     iterationsCounter -= 1;
   }
 
-  return fib;
+  return fibSequence;
 }

src/algorithms/math/fibonacci/fibonacciNth.js

@@ -0,0 +1,20 @@
+// Calculate fibonacci number at specific position using Dynamic Programming approach.
+export default function fibonacciNth(n) {
+  let currentValue = 1;
+  let previousValue = 0;
+
+  if (n === 1) {
+    return 1;
+  }
+
+  let iterationsCounter = n - 1;
+
+  while (iterationsCounter) {
+    currentValue += previousValue;
+    previousValue = (currentValue - previousValue);
+
+    iterationsCounter -= 1;
+  }
+
+  return currentValue;
+}