feat: fibonacci algorithm

src/algorithms/fibonacci/fibonacci.ts

@@ -0,0 +1,41 @@
+// Option 1
+export const fibonacci = (n: number) => {
+  const result = [0, 1];
+
+  for (let i = 2; i <= n; i++) {
+    const a = result[i - 1];
+    const b = result[i - 2];
+
+    result.push(a + b);
+  }
+
+  return result[n];
+};
+
+const memoize = (fn: (n: number) => number) => {
+  const cache: { [key: string]: number } = {};
+
+  return function (...args: number[]) {
+    const key = JSON.stringify(args);
+
+    if (cache[key]) {
+      return cache[key];
+    }
+
+    const result = fn.apply(this, args);
+    cache[key] = result;
+
+    return result;
+  };
+};
+
+const slowFib = (n: number) => {
+  if (n < 2) {
+    return n;
+  }
+
+  return memoizedFib(n - 1) + memoizedFib(n - 2);
+};
+
+// Option 2
+export const memoizedFib = memoize(slowFib);

src/algorithms/fibonacci/tests/fibonacci.test.ts

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+import { fibonacci, memoizedFib } from '../fibonacci';
+
+describe('Fibonacci Algorithm', () => {
+  test('Fib function is defined', () => {
+    expect(typeof fibonacci).toEqual('function');
+    expect(typeof memoizedFib).toEqual('function');
+  });
+
+  test('calculates correct fibonacci value for 1', () => {
+    expect(fibonacci(1)).toEqual(1);
+    expect(memoizedFib(1)).toEqual(1);
+  });
+
+  test('calculates correct fibonacci value for 2', () => {
+    expect(fibonacci(2)).toEqual(1);
+    expect(memoizedFib(2)).toEqual(1);
+  });
+
+  test('calculates correct fibonacci value for 3', () => {
+    expect(fibonacci(3)).toEqual(2);
+    expect(memoizedFib(3)).toEqual(2);
+  });
+
+  test('calculates correct fibonacci value for 4', () => {
+    expect(fibonacci(4)).toEqual(3);
+    expect(memoizedFib(4)).toEqual(3);
+  });
+
+  test('calculates correct fibonacci value for 15', () => {
+    expect(fibonacci(39)).toEqual(63245986);
+    expect(memoizedFib(39)).toEqual(63245986);
+  });
+});