Flatten Arbitrarily Nested Lists (Recursion) プログラミングチャレンジ

問題

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.

制約

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.

例

例 1

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

期待される出力：
expected = [1, 2, 3, 4]

スターターコードで提供されている NestedValue 型を使ってください。フィールドは kind（0 = null、1 = 整数、2 = リスト）、value（整数値）、items（ネストされたリスト）です。

入力：
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, {}}
};

期待される出力：
std::vector<long long> expected = {1, 2, 3, 4};

入力：
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 }
};

期待される出力：
long[] expected = new long[] {1, 2, 3, 4};

解説

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

例 2

入力：
values = [
    None,
    [],
    [None]
]

期待される出力：
expected = []

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

期待される出力：
std::vector<long long> expected = {};

入力：
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 }
    } }
};

期待される出力：
long[] expected = new long[] {};

解説

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

参考資料

この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。

Exercism: Flatten Array

Flatten Arbitrarily Nested Lists (Recursion)

問題

Input

Output

制約

例

解説

解説

参考資料

コミュニティの解答