Задача: Flatten Arbitrarily Nested Lists (Recursion)

Условие

This is the advanced follow-up to Flatten a 2D Array. Practice that challenge first. Here lists may contain more lists at any depth. In C++ and C#, use the NestedValue type in the starter code. Read kind first: 0 means skip this entry, 1 means append value, and 2 means visit items recursively.

Turn a nested list into a flat list of integers. Read from left to right; whenever you reach another list, read its contents before continuing. Ignore null values (shown as None in examples) and empty lists. Preserve repeated integers and their order.

Python receives ordinary nested lists containing integers and None. C++ and C# receive a list of NestedValue objects supplied by the starter: kind 0 means null, kind 1 means integer in value, and kind 2 means a list in items. Only the field selected by kind matters. Return a plain integer list in every language.

Implement flatten_arbitrarily_nested_list(values).

Input

values: A list whose entries can be integers, null, or further lists.

Output

Return the integers in depth-first, left-to-right order. Return an empty list when there are no integers.

Ограничения

The outer value is a list. At most 10,000 entries across all lists; maximum nesting depth 50. Integer leaves fit signed 64-bit. Leaves are integers or null, never strings or booleans.

Примеры

Пример 1

Ввод:
values = [
    1,
    [
        2,
        None,
        [3]
    ],
    [],
    4
]

Ожидаемый вывод:
expected = [1, 2, 3, 4]

Используйте тип NestedValue из стартового кода. Его поля: kind (0 = null, 1 = integer, 2 = list), value (целое число) и items (вложенный список).

Ввод:
std::vector<NestedValue> values = {
    NestedValue{1, 1, {}},
    NestedValue{2, 0, {
        NestedValue{1, 2, {}},
        NestedValue{0, 0, {}},
        NestedValue{2, 0, {
            NestedValue{1, 3, {}}
        }}
    }},
    NestedValue{2, 0, {}},
    NestedValue{1, 4, {}}
};

Ожидаемый вывод:
std::vector<long long> expected = {1, 2, 3, 4};

Ввод:
NestedValue[] values = new NestedValue[] {
    new NestedValue { kind = 1, value = 1 },
    new NestedValue { kind = 2, items = new NestedValue[] {
        new NestedValue { kind = 1, value = 2 },
        new NestedValue { kind = 0 },
        new NestedValue { kind = 2, items = new NestedValue[] {
            new NestedValue { kind = 1, value = 3 }
        } }
    } },
    new NestedValue { kind = 2, items = new NestedValue[] {} },
    new NestedValue { kind = 1, value = 4 }
};

Ожидаемый вывод:
long[] expected = new long[] {1, 2, 3, 4};

Пояснение

Read 1, then enter the nested list and read 2 and 3, skipping null. The empty list adds nothing; finish with 4.

Пример 2

Ввод:
values = [
    None,
    [],
    [None]
]

Ожидаемый вывод:
expected = []

Ввод:
std::vector<NestedValue> values = {
    NestedValue{0, 0, {}},
    NestedValue{2, 0, {}},
    NestedValue{2, 0, {
        NestedValue{0, 0, {}}
    }}
};

Ожидаемый вывод:
std::vector<long long> expected = {};

Ввод:
NestedValue[] values = new NestedValue[] {
    new NestedValue { kind = 0 },
    new NestedValue { kind = 2, items = new NestedValue[] {} },
    new NestedValue { kind = 2, items = new NestedValue[] {
        new NestedValue { kind = 0 }
    } }
};

Ожидаемый вывод:
long[] expected = new long[] {};

Пояснение

Every entry is null or an empty container. No integer remains.

Ссылки

Это задание адаптировано для CodeUtility. Следуйте условию и ограничениям выше.

Exercism: Flatten Array

Flatten Arbitrarily Nested Lists (Recursion)

Условие

Input

Output

Ограничения

Примеры

Пояснение

Пояснение

Ссылки

Решения сообщества