28: number spiral diagonals

28_number_spiral_diagonals/main.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+)
+
+func main() {
+	nums, _ := findSprialDiagonals(1001)
+	sum := 0
+	for _, n := range nums {
+		sum += n
+	}
+	fmt.Printf("nums=%v\nsum=%d\n", nums, sum)
+}
+
+func findSprialDiagonals(width int) ([]int, error) {
+	if width%2 == 0 {
+		return nil, errors.New("invalid width")
+	}
+	x := 3
+	ret := []int{1}
+	cw := 3
+	d := 2
+	for width/cw > 0 {
+		ret = append(ret, []int{x, x + d, x + 2*d, x + 3*d}...)
+		x = x + 3*d + cw + 1
+		cw += 2
+		d = cw - 1
+	}
+	return ret, nil
+}

28_number_spiral_diagonals/main_test.go

@@ -0,0 +1,61 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func Test_findSprialDiagonals(t *testing.T) {
+	type args struct {
+		width int
+	}
+	tests := []struct {
+		name    string
+		args    args
+		want    []int
+		wantErr bool
+	}{
+		{
+			"1",
+			args{1},
+			[]int{1},
+			false,
+		},
+		{
+			"2",
+			args{2},
+			nil,
+			true,
+		},
+		{
+			"3",
+			args{3},
+			[]int{1, 3, 5, 7, 9},
+			false,
+		},
+		{
+			"5",
+			args{5},
+			[]int{1, 3, 5, 7, 9, 13, 17, 21, 25},
+			false,
+		},
+		{
+			"7",
+			args{7},
+			[]int{1, 3, 5, 7, 9, 13, 17, 21, 25, 31, 37, 43, 49},
+			false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := findSprialDiagonals(tt.args.width)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("findSprialDiagonals() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("findSprialDiagonals() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}