24: pandigital products

24_lexicographic_permutations/main.go

@@ -10,7 +10,7 @@ var nums = []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
 func main() {
 	var facs []int
 	for _, i := range nums {
-		n, _ := findPermutation(i, i)
+		n := findFacs(i)
 		facs = append(facs, n)
 	}
 	fmt.Println("facs:", facs)
@@ -30,13 +30,10 @@ func findNPermutation(n int, src []int, facs []int) string {
 	return ret
 }
 
-func findPermutation(n, m int) (int, error) {
-	if m > n {
-		return 0, fmt.Errorf("m=%d cannot be larger than n=%d", m, n)
-	}
+func findFacs(n int) int {
 	p := 1
-	for i := n - m + 1; i <= n; i++ {
+	for i := 1; i <= n; i++ {
 		p *= i
 	}
-	return p, nil
+	return p
 }

24_lexicographic_permutations/main_test.go

@@ -1,67 +1,44 @@
 package main
 
 import (
-	"errors"
-	"reflect"
 	"testing"
 )
 
 func Test_findPermutation(t *testing.T) {
 	type args struct {
 		n int
-		m int
 	}
 	tt := []struct {
-		name    string
-		args    args
-		want    int
-		wantErr error
+		name string
+		args args
+		want int
 	}{
 		{
-			"1-2",
-			args{1, 2},
-			0,
-			errors.New("m=2 cannot be larger than n=1"),
-		},
-		{
-			"1-1",
-			args{1, 1},
+			"1",
+			args{1},
 			1,
-			nil,
 		},
 		{
-			"3-3",
-			args{3, 3},
+			"2",
+			args{1},
+			2,
+		},
+		{
+			"3",
+			args{3},
 			6,
-			nil,
 		},
 		{
-			"4-4",
-			args{4, 4},
+			"4",
+			args{4},
 			24,
-			nil,
-		},
-		{
-			"3-2",
-			args{3, 2},
-			6,
-			nil,
-		},
-		{
-			"4-2",
-			args{4, 2},
-			12,
-			nil,
 		},
 	}
 	for _, tc := range tt {
 		t.Run(tc.name, func(t *testing.T) {
-			got, err := findPermutation(tc.args.n, tc.args.m)
-			if !reflect.DeepEqual(err, tc.wantErr) {
-				t.Errorf("findPermutation() = %v, want err %v", err, tc.wantErr)
-			}
+			got := findFacs(tc.args.n)
 			if got != tc.want {
-				t.Errorf("findPermutation() = %v, want %v", got, tc.want)
+				t.Errorf("findFacs() = %v, want %v", got, tc.want)
 			}
 		})
 	}

32_pandigital_products/main.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+)
+
+func main() {
+	sum := 0
+	for i := 0; i < 10000; i++ {
+		if hasPandigitalProduct(i) {
+			sum += i
+		}
+	}
+	fmt.Println("sum:", sum)
+}
+
+func hasPandigitalProduct(n int) bool {
+	for i := 1; i <= n; i++ {
+		for n%i == 0 && isPandigital(strconv.Itoa(n)+strconv.Itoa(i)+strconv.Itoa(n/i)) {
+			fmt.Printf("Pandigital:%d = %d * %d\n", n, i, n/i)
+			return true
+		}
+	}
+	return false
+}
+
+func isPandigital(s string) bool {
+	var ss []string
+	for _, c := range s {
+		ss = append(ss, string(c))
+	}
+	sort.Strings(ss)
+	s = ""
+	for _, c := range ss {
+		s += c
+	}
+	return s == "123456789"
+}

32_pandigital_products/main_test.go

@@ -0,0 +1,63 @@
+package main
+
+import (
+	"testing"
+)
+
+func Test_isPandigital(t *testing.T) {
+	type args struct {
+		s string
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			"912345678",
+			args{"912345678"},
+			true,
+		},
+		{
+			"12345678",
+			args{"12345678"},
+			false,
+		},
+		{
+			"812349756",
+			args{"812349756"},
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := isPandigital(tt.args.s); got != tt.want {
+				t.Errorf("isPandigital() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_hasPandigitalProduct(t *testing.T) {
+	type args struct {
+		n int
+	}
+	tests := []struct {
+		name string
+		args args
+		want bool
+	}{
+		{
+			"7254",
+			args{7254},
+			true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := hasPandigitalProduct(tt.args.n); got != tt.want {
+				t.Errorf("hasPandigitalProduct() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}