Homework

exercises/fibonacci/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"fmt"
+)
+
+func fibonacci(n, n1, n2 int) {
+	if n == 0 {
+		return
+	}
+	fmt.Printf("%v ", n2)
+	fibonacci(n-1, n2, n1+n2)
+}
+
+func main() {
+	fibonacci(1, 0, 1)
+	fmt.Println()
+	fibonacci(2, 0, 1)
+	fmt.Println()
+	fibonacci(3, 0, 1)
+	fmt.Println()
+	fibonacci(4, 0, 1)
+	fmt.Println()
+	fibonacci(5, 0, 1)
+	fmt.Println()
+	fibonacci(6, 0, 1)
+	fmt.Println()
+	fibonacci(7, 0, 1)
+}
+
+// Time complexity: O(n)
+// Space complexity: O(n)

exercises/isPowerOf2/main.go

@@ -0,0 +1,17 @@
+package main
+
+import "fmt"
+
+func isPowerOf2(n int) {
+	if n%2 == 1 && n != 1 {
+		fmt.Println("NO")
+		return
+	} else if n == 1 {
+		fmt.Println("YES")
+		return
+	}
+	isPowerOf2(n / 2)
+}
+
+// Time complexity: O(log(n))
+// Space complexity: O(log(n))

exercises/main.go

@@ -0,0 +1,21 @@
+package main
+
+func rearrange(s []int, pivot int) (i int) {
+	l, r, p := 0, len(s)-1, s[pivot]
+	for {
+		for s[l] < p {
+			l++
+		}
+		for s[r] > p {
+			r--
+		}
+		if l >= r {
+			return r
+		}
+		if s[l] != s[r] {
+			s[l], s[r] = s[r], s[l]
+		} else {
+			r--
+		}
+	}
+}

exercises/main_test.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestRearrange(t *testing.T) {
+	for _, tc := range []struct {
+		name  string
+		s     []int
+		pivot int
+		want  int
+	}{
+		{"no repeated elements", []int{8, 4, 1, 0, 5, 9, 3, 7, 2, 6}, 4, 5},
+		{"repeated elements", []int{9, 6, 1, 7, 5, 9, 6, 5, 2, 6}, 9, 4},
+		{"empty left side", []int{9, 6, 1, 7, 5, 9, 6, 5, 2, 0}, 9, 0},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			got := rearrange(tc.s, tc.pivot)
+			areLess(tc.s[:got], tc.s[got], t)
+			if got != tc.want {
+				t.Errorf("got = %v, want = %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func areLess(s []int, p int, t *testing.T) {
+	for _, e := range s {
+		if e > p {
+			t.Errorf("%v > %v", e, p)
+		}
+	}
+}

exercises/maxNumber/main.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+)
+
+func max(s []int, i, max1, max2 int) {
+	if i == len(s) {
+		fmt.Println(max1, max2)
+		return
+	}
+	if max2 < s[i] && s[i] <= max1 {
+		max2 = s[i]
+	} else if max1 < s[i] {
+		max1, max2 = s[i], max1
+	}
+	max(s, i+1, max1, max2)
+}
+
+// Time complexity: O(n)
+// Space complexity: O(n)

exercises/numbers/main.go

@@ -0,0 +1,15 @@
+package main
+
+import "fmt"
+
+func print(n int) {
+	if n == 0 {
+		return
+	}
+	fmt.Println(n)
+	print(n - 1)
+	fmt.Println(n)
+}
+
+// Time complexity: O(n)
+// Space complexity: O(n)

exercises/sumDigits/main.go

@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+)
+
+func sumDigits(n, sum int) {
+	if n == 0 {
+		fmt.Println(sum)
+		return
+	}
+	sum += n % 10
+	sumDigits(n/10, sum)
+}
+
+func main() {
+	sumDigits(123, 0)
+	sumDigits(987, 0)
+	sumDigits(12345, 0)
+	sumDigits(12357, 0)
+}
+
+// Time complexity: O(n)
+// Space complexity: O(n)