Add fibonacci algorithm by dynamic programming (#252)

* Add fibonacci algorithm by dynamic programming

* Improve fibonacci.go implementation

* Add test for NthFibonacci function

* Put the test runs inside test cases loop

Author: IanvsPoplicola

dynamicprogramming/fibonacc_test.go

@@ -0,0 +1,42 @@
+package dynamicprogramming
+
+import (
+	"fmt"
+	"testing"
+)
+
+func Test_NthFibonacci(t *testing.T) {
+	// source: http://www.maths.surrey.ac.uk/hosted-sites/R.Knott/Fibonacci/fibtable.html
+	var fibonacciNumbers = []struct {
+		nth       uint
+		fibonacci uint
+	}{
+		{0, 0},
+		{1, 1},
+		{2, 1},
+		{3, 2},
+		{4, 3},
+		{5, 5},
+		{6, 8},
+		{7, 13},
+		{8, 21},
+		{9, 34},
+		{10, 55},
+		{20, 6765},
+		{30, 832040},
+		{40, 102334155},
+		{50, 12586269025},
+		{60, 1548008755920},
+		{70, 190392490709135},
+		{80, 23416728348467685},
+		{90, 2880067194370816120},
+	}
+	for i := range fibonacciNumbers {
+		t.Run(fmt.Sprintf("the %dth Fibonacci number", fibonacciNumbers[i].nth), func(t *testing.T) {
+			result := NthFibonacci(fibonacciNumbers[i].nth)
+			if result != fibonacciNumbers[i].fibonacci {
+				t.Errorf("Expected the %dth Fibonacci number to be %d, got %d", fibonacciNumbers[i].nth, fibonacciNumbers[i].fibonacci, result)
+			}
+		})
+	}
+}

dynamicprogramming/fibonacci.go

@@ -0,0 +1,21 @@
+package dynamicprogramming
+
+// https://www.geeksforgeeks.org/program-for-nth-fibonacci-number/
+
+// NthFibonacci returns the nth Fibonacci Number
+func NthFibonacci(n uint) uint {
+	if n == 0 {
+		return 0
+	}
+
+	// n1 and n2 are the (i-1)th and ith Fibonacci numbers, respectively
+	var n1, n2 uint = 0, 1
+
+	for i := uint(1); i < n; i++ {
+		n3 := n1 + n2
+		n1 = n2
+		n2 = n3
+	}
+
+	return n2
+}