Create Fibonacci.js

maths/Fibonacci.js

@@ -0,0 +1,59 @@
+const list = []
+
+const FibonacciIterative = (nth) => {
+  const sequence = []
+
+  if (nth >= 1) sequence.push(1)
+  if (nth >= 2) sequence.push(1)
+
+  for (let i = 2; i < nth; i++) {
+    sequence.push(sequence[i - 1] + sequence[i - 2])
+  }
+
+  return sequence
+}
+
+const FibonacciRecursive = (number) => {
+  return (() => {
+    switch (list.length) {
+      case 0:
+        list.push(1)
+        return FibonacciRecursive(number)
+      case 1:
+        list.push(1)
+        return FibonacciRecursive(number)
+      case number:
+        return list
+      default:
+        list.push(list[list.length - 1] + list[list.length - 2])
+        return FibonacciRecursive(number)
+    }
+  })()
+}
+
+const dict = new Map()
+
+const FibonacciRecursiveDP = (stairs) => {
+  if (stairs <= 0) return 0
+  if (stairs === 1) return 1
+
+  // Memoize stair count
+  if (dict.has(stairs)) return dict.get(stairs)
+
+  const res =
+    FibonacciRecursiveDP(stairs - 1) + FibonacciRecursiveDP(stairs - 2)
+
+  dict.set(stairs, res)
+
+  return res
+}
+
+// testing
+
+console.log(FibonacciIterative(5))
+// Output: [ 1, 1, 2, 3, 5 ]
+console.log(FibonacciRecursive(5))
+// Output: [ 1, 1, 2, 3, 5 ]
+
+console.log(FibonacciRecursiveDP(5))
+// Output: 5