24: lexicographic permutations

24_lexicographic_permutations/main_test.go

@@ -0,0 +1,109 @@
+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
+	}{
+		{
+			"1-2",
+			args{1, 2},
+			0,
+			errors.New("m=2 cannot be larger than n=1"),
+		},
+		{
+			"1-1",
+			args{1, 1},
+			1,
+			nil,
+		},
+		{
+			"3-3",
+			args{3, 3},
+			6,
+			nil,
+		},
+		{
+			"4-4",
+			args{4, 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)
+			}
+			if got != tc.want {
+				t.Errorf("findPermutation() = %v, want %v", got, tc.want)
+			}
+		})
+	}
+}
+
+func Test_findNPermutation(t *testing.T) {
+	type args struct {
+		n    int
+		src  []int
+		facs []int
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			"012-1",
+			args{1, []int{0, 1, 2}, []int{1, 1, 2}},
+			"012",
+		},
+		{
+			"012-2",
+			args{2, []int{0, 1, 2}, []int{1, 1, 2}},
+			"021",
+		},
+		{
+			"012-6",
+			args{6, []int{0, 1, 2}, []int{1, 1, 2}},
+			"210",
+		},
+		{
+			"0123456-1",
+			args{1, []int{0, 1, 2, 3, 4, 5, 6}, []int{1, 1, 2, 6, 24, 120, 720}},
+			"0123456",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := findNPermutation(tt.args.n, tt.args.src, tt.args.facs); got != tt.want {
+				t.Errorf("findNPermutation() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}