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danny-andrews/recursive-reverse.js

Last active July 6, 2021 16:50
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Revisions

  1. danny-andrews revised this gist Jul 6, 2021. 1 changed file with 10 additions and 38 deletions.
    48 changes: 10 additions & 38 deletions recursive-reverse.js
    View file
    Original file line number Diff line number Diff line change
    @@ -7,42 +7,14 @@ const reverseIterative = (arr) => {
    return result;
    };

    const reverseMutating = (arr) => {
    if (arr.length === 0) return [];

    const last = arr.pop();

    return [last].concat(reverseMutating(arr));
    };

    const reverseSlice = (arr) =>
    arr.length === 0 ? [] : arr.slice(-1).concat(reverseSlice(arr.slice(0, -1)));

    const reverseES6 = ([head, ...tail]) => {
    if (!head) return [];

    return [...reverseES6(tail), head];
    };

    const reverseTurboMode = ([head, ...tail]) =>
    !head ? [] : [...reverseTurboMode(tail), head];

    const methods = [
    reverseIterative,
    reverseSlice,
    reverseES6,
    reverseTurboMode,
    reverseMutating,
    ];

    const input = [1, 2, 3, undefined, 4, 5];
    methods.forEach((method) => {
    console.log(method(input));
    });

    // reverseSlice([1, 2, 3]);
    // [3] + reverseSlice([1, 2])
    // [3] + [2] + reverseSlice([1])
    // [3] + [2] + [1] + reverseSlice([])
    // [3] + [2] + [1] + []
    const reverseRec = (arr) =>
    arr.length === 0 ? [] : arr.slice(-1).concat(reverseRec(arr.slice(0, -1)));

    // reverseRec([1, 2, 3]);
    // [3] + reverseRec([1, 2])
    // [3] + ([2] + reverseRec([1]))
    // [3] + ([2] + ([1] + reverseRec([])))
    // [3] + ([2] + ([1] + []))
    // [3] + ([2] + [1])
    // [3] + [2, 1]
    // [3, 2, 1]
  2. danny-andrews revised this gist Jul 6, 2021. 1 changed file with 7 additions and 0 deletions.
    7 changes: 7 additions & 0 deletions recursive-reverse.js
    View file
    Original file line number Diff line number Diff line change
    @@ -39,3 +39,10 @@ const input = [1, 2, 3, undefined, 4, 5];
    methods.forEach((method) => {
    console.log(method(input));
    });

    // reverseSlice([1, 2, 3]);
    // [3] + reverseSlice([1, 2])
    // [3] + [2] + reverseSlice([1])
    // [3] + [2] + [1] + reverseSlice([])
    // [3] + [2] + [1] + []
    // [3, 2, 1]
  3. danny-andrews created this gist Jul 6, 2021.
    41 changes: 41 additions & 0 deletions recursive-reverse.js
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,41 @@
    const reverseIterative = (arr) => {
    const result = [];
    for (let i = arr.length - 1; i >= 0; i--) {
    result.push(arr[i]);
    }

    return result;
    };

    const reverseMutating = (arr) => {
    if (arr.length === 0) return [];

    const last = arr.pop();

    return [last].concat(reverseMutating(arr));
    };

    const reverseSlice = (arr) =>
    arr.length === 0 ? [] : arr.slice(-1).concat(reverseSlice(arr.slice(0, -1)));

    const reverseES6 = ([head, ...tail]) => {
    if (!head) return [];

    return [...reverseES6(tail), head];
    };

    const reverseTurboMode = ([head, ...tail]) =>
    !head ? [] : [...reverseTurboMode(tail), head];

    const methods = [
    reverseIterative,
    reverseSlice,
    reverseES6,
    reverseTurboMode,
    reverseMutating,
    ];

    const input = [1, 2, 3, undefined, 4, 5];
    methods.forEach((method) => {
    console.log(method(input));
    });