How to convert a linear structure to a hierarchical one?

Question

JavaScript

There is a simple linear array. Example:

[
    { level: 0},
    { level: 1},
    { level: 2},
    { level: 1},
    { level: 2},
    { level: 1},
    { level: 2},
    { level: 3},
    { level: 3},
    { level: 4},
    { level: 2}
]

Need to make a hierarchy based on levels. For the current example, it will be like this:

{
    level: 0,
    content: [
        {
            level: 1,
            content: [
                {
                    level: 2
                }
            ]
        },
        {
            level: 1,
            content: [
                {
                    level: 2
                }
            ]
        },
        {
            level: 1,
            content: [
                {
                    level: 2,
                    content: [
                        {
                            level: 3
                        },
                        {
                            level: 3,
                            content: [
                                {
                                    level: 4
                                }
                            ]
                        }
                    ]
                },
                {
                    level: 2
                }
            ]
        }
    ]
}

Help me write an algorithm.

Answer 1

https://jsfiddle.net/3y4ewh20

Answer 2

I would suggest recursion. Everything that is returned by deeper recursion calls, as well as single (without children) nodes of the current level, we hook up to one level. As soon as we met a level higher than the current one in the linear array, we complete the recursive procedure and feed the resulting array as the result of the call (it will be a node for a higher-level array).