chore: add problem down to zero

datastructures/down_to_zero_ii.go

@@ -0,0 +1,71 @@
+package datastructures
+
+// https://www.hackerrank.com/challenges/down-to-zero-ii/problem
+
+// !! Needs optimization to pass all tests !!
+
+type DownToZeroQueue struct {
+	items []*DownToZeroItem
+}
+
+type DownToZeroItem struct {
+	value int32
+	step  int32
+}
+
+func (q *DownToZeroQueue) isEmpty() bool                 { return len(q.items) == 0 }
+func (q *DownToZeroQueue) enqueue(value *DownToZeroItem) { q.items = append(q.items, value) }
+func (q *DownToZeroQueue) dequeue() *DownToZeroItem {
+	if len(q.items) == 0 {
+		return nil
+	}
+	result := q.items[0]
+	q.items = q.items[1:]
+	return result
+}
+
+func downToZero(n int32) int32 {
+	visited := make(map[int32]bool)
+	queue := &DownToZeroQueue{}
+	queue.enqueue(&DownToZeroItem{
+		value: 1,
+		step:  1,
+	})
+
+	for !queue.isEmpty() {
+		item := queue.dequeue()
+		if visited[item.value] {
+			continue
+		}
+
+		visited[item.value] = true
+
+		if item.value+1 == n {
+			return item.step + 1
+		}
+
+		if item.value+1 < n {
+			queue.enqueue(&DownToZeroItem{
+				value: item.value + 1,
+				step:  item.step + 1,
+			})
+		}
+
+		for i := 2; i <= int(item.value); i++ {
+			if i*int(item.value) > int(n) {
+				break
+			}
+
+			if item.value*int32(i) == n {
+				return item.step + 1
+			}
+
+			queue.enqueue(&DownToZeroItem{
+				value: item.value * int32(i),
+				step:  item.step + 1,
+			})
+		}
+	}
+
+	return 1
+}

datastructures/down_to_zero_ii_test.go

@@ -0,0 +1,72 @@
+package datastructures
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+type DownToZeroIITestCase struct {
+	n      int32
+	result int32
+}
+
+func TestDownToZeroII(t *testing.T) {
+	tests := []DownToZeroIITestCase{
+		{n: 3, result: 3},
+		{n: 4, result: 3},
+		{n: 10, result: 5},
+		{n: 266574, result: 8},
+		{n: 603900, result: 7},
+		{n: 847224, result: 7},
+		{n: 484982, result: 9},
+		{n: 937693, result: 8},
+		{n: 596249, result: 9},
+		{n: 991347, result: 9},
+		{n: 872132, result: 9},
+		{n: 386794, result: 8},
+		{n: 302076, result: 9},
+		{n: 51784, result: 9},
+		{n: 373072, result: 9},
+		{n: 580459, result: 9},
+		{n: 894812, result: 9},
+		{n: 42386, result: 9},
+		{n: 633287, result: 10},
+		{n: 309619, result: 9},
+		{n: 549380, result: 8},
+		{n: 667351, result: 10},
+		{n: 314003, result: 9},
+		{n: 855076, result: 9},
+		{n: 472574, result: 11},
+		{n: 332264, result: 8},
+		{n: 299566, result: 8},
+		{n: 344188, result: 10},
+		{n: 556652, result: 8},
+		{n: 226615, result: 10},
+		{n: 802657, result: 9},
+		{n: 5, result: 4},
+		{n: 10, result: 5},
+		{n: 5, result: 4},
+		{n: 1, result: 1},
+		{n: 1, result: 1},
+		{n: 10, result: 5},
+		{n: 10, result: 5},
+		{n: 7, result: 5},
+		{n: 8, result: 4},
+		{n: 8, result: 4},
+		{n: 8, result: 4},
+		{n: 4, result: 3},
+		{n: 1, result: 1},
+		{n: 2, result: 2},
+		{n: 4, result: 3},
+		{n: 4, result: 3},
+		{n: 9, result: 4},
+		{n: 2, result: 2},
+		{n: 9, result: 4},
+		{n: 3, result: 3},
+	}
+
+	for _, test := range tests {
+		assert.Equal(t, test.result, downToZero(test.n))
+	}
+}