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Go のリスト分割

Last updated at Posted at 2024-08-13

リストを指定のサイズで分割して返す関数を用意した。
誰かが使うかも知れないので、共有しておく。誰も使わなかったら自分で使おう。

func Split[T any](elms []T, size int) [][]T {
	if size <= 0 {
		return [][]T{elms}
	}
	var split [][]T
	for 0 < len(elms) {
		s := size
		if len(elms) < size {
			s = len(elms)
		}
		split = append(split, elms[0:s])
		elms = elms[s:]
	}
	return split
}

テストケースも併せて用意。

func TestSplit(t *testing.T) {
	tests := []struct {
		name string
		elms []string
		size int
		want [][]string
	}{
		{
			name: "partial",
			elms: []string{"a", "b", "c", "d", "e"},
			size: 2,
			want: [][]string{{"a", "b"}, {"c", "d"}, {"e"}},
		},
		{
			name: "just",
			elms: []string{"a", "b", "c", "d", "e", "f"},
			size: 2,
			want: [][]string{{"a", "b"}, {"c", "d"}, {"e", "f"}},
		},
		{
			name: "single element",
			elms: []string{"a"},
			size: 2,
			want: [][]string{{"a"}},
		},
		{
			name: "empty",
			elms: []string{},
			size: 2,
			want: nil,
		},
		{
			name: "nil",
			elms: nil,
			size: 2,
			want: nil,
		},
		{
			name: "size: 1",
			elms: []string{"a", "b", "c", "d", "e"},
			size: 1,
			want: [][]string{{"a"}, {"b"}, {"c"}, {"d"}, {"e"}},
		},
		{
			name: "size: 0",
			elms: []string{"a", "b", "c", "d", "e"},
			size: 0,
			want: [][]string{{"a", "b", "c", "d", "e"}},
		},
		{
			name: "size: -1",
			elms: []string{"a", "b", "c", "d", "e"},
			size: 0,
			want: [][]string{{"a", "b", "c", "d", "e"}},
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := Split(tt.elms, tt.size)
			if !reflect.DeepEqual(got, tt.want) {
				t.Errorf("Split() = %v, want %v", got, tt.want)
			}
		})
	}
}

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