Create Nested List from Multidimensional Array

Create nested list from Multidimensional Array

You should use recursion:

First the array in 'php' syntax:

<?php
$a=array (
    '0' => array (
        'id' => 1,
        'title' => "Title 1",
        'parent_id' => 'NULL',
        'depth' => 0
    ),
    '1' => array (
        'id' => 2,
        'title' => "Title 2",
        'parent_id' => 'NULL',
        'depth' => 0
    ),
    '2' => array (
        'id' => 3,
        'title' => "Title 3",
        'parent_id' => 2,
        'depth' => 1
    ),
    '3' => array (
        'id' => 4,
        'title' => "Title 4",
        'parent_id' => 2,
        'depth' => 1
    ),
    '4' => array (
        'id' => 5,
        'title' => "Title 5",
        'parent_id' => 'NULL',
        'depth' => 0
    ),
    '5' => array (
        'id' => 6,
        'title' => "Title 6",
        'parent_id' => 4,
        'depth' => 0
    )
);

Here the code:

$level = 'NULL';

function r( $a, $level) {
   $r = "<ol>";
   foreach ( $a as $i ) {
       if ($i['parent_id'] == $level ) {
          $r = $r . "<li>" . $i['title'] . r( $a, $i['id'] ) . "</li>";
       }
   }
   $r = $r . "</ol>";
   return $r;
}

print r( $a, $level );

?>

The results:

<ol><li>Title 1<ol></ol></li><li>Title 2<ol><li>Title 3<ol>
</ol></li><li>Title 4<ol><li>Title 6<ol></ol></li></ol></li></ol></li><li>Title 5
<ol></ol></li></ol>

1. Title 1\n
2. Title 2\n
   1. Title 3\n
   2. Title 4\n
      1. Title 6\n
3. Title 5\n

EDITED AFTER CHECK AS SOLUTION

To avoid empty leafs:

function r( $a, $level) {
   $r = '' ;
   foreach ( $a as $i ) {
       if ($i['parent_id'] == $level ) {
          $r = $r . "<li>" . $i['title'] . r( $a, $i['id'] ) . "</li>";
       }
   }
   return ($r==''?'':"<ol>". $r . "</ol>");
}

Nested list from two-dimensional Array

The problem is that after processing the first item at the base layer, you then return inside the foreach loop which means that it won't go onto any further items.

Instead you need to build up all of the output and return this from the end of the function...

function extractLayer($parent, $arrayAllObjects){
    $output = "";
    foreach ($arrayAllObjects as $object) {
        if ($object["parent"]==$parent) {
            $subLayer = extractLayer($object["ID"], $arrayAllObjects);
            if ( !empty($subLayer) )    {
                $output .="<ul>".$object["name"].$subLayer."</ul>";
            }
            else    {
                $output .= "<li>".$object["name"]."</li>";
            }
        }
    }
    return $output;
}

echo extractLayer("0", $allObjects);

I've also changed the function name as r isn't obvious.

Just updated this as each leaf was also building a list of it's own even if there were no sub layers. So this checks for sub layers and if there aren't any, it just puts the item in <li> tags.

How to replace a nested list in multi-dimensional array python with another list based on a certain condition

Try like this:

my_list = [
    [[["", ""], ["HB2_DF_en1a", "HB2_DF_en2a"]]],
    [[[""], ["XY1_DF_en1a"]], [["Io01[4:2]"], ["XY_DF1"]]],
    [[["", ""], ["XY2_DF_en1a", "XY2_DF_en2a"]]],
]
reference_list = [
    ["XY1_IPC"],
    ["cat_lpm"],
    ["XY_ABC1"],
    ["XY2_IPC"],
    ["XY_ABC2", "XY2_IPC"],
]

ref_index = 0
for level1 in my_list:
    for level2 in level1:
        for index, value in enumerate(level2):
            if value[0] == "":
                for change_index, times in enumerate(value):
                    level2[1][change_index] = reference_list[ref_index]
                    ref_index = ref_index + 1

# Print result:
print(my_list)

Result:

[
    [
        [
            ['', ''],
            [
                ['XY1_IPC'],
                ['cat_lpm']
            ]
        ]
    ],
    [
        [
            [''],
            [
                ['XY_ABC1']
            ]
        ],
        [
            ['Io01[4:2]'],
            ['XY_DF1']
        ]
    ],
    [
        [
            ['', ''],
            [
                ['XY2_IPC'],
                ['XY_ABC2', 'XY2_IPC']
            ]
        ]
    ]
] 

Converting Julia nested list to multidimensional array

hcat works fine:

julia> hcat([[1,2],[4,5]]...)
2×2 Matrix{Int64}:
 1  4
 2  5

The thing is that vectors are column-vectors in Julia (unlike in NumPy, for example), so you should horisontally concatenate them to get the matrix.

If you use vcat, you'll stack them on top of each other, getting one tall vector:

julia> vcat([[1,2],[4,5]]...)
4-element Vector{Int64}:
 1
 2
 4
 5

Convert nested list to 2d array

There is no simple builtin way to do what you want because your list.toArray() can return only array of elements stored in list which in your case would also be lists.

Simplest solution would be creating two dimensional array and filling it with results of toArray from each of nested lists.

String[][] array = new String[list.size()][];

int i = 0;
for (List<String> nestedList : list) {
    array[i++] = nestedList.toArray(new String[0]);
}

(you can shorten this code if you are using Java 8 with streams just like Alex did)

Nested list or two dimensional array in Python

You can use collections.Counter to count each IP-{number} line from the file:

from collections import Counter

with open("test.txt") as f:
    ip_counts = Counter(line.strip() for line in f)
    # Counter({'IP-4': 3, 'IP-2': 2, 'IP-1': 1, 'IP-7': 1})

    for ip_address, count in ip_counts.items():
        print("IP address %s occured %d times" % (ip_address, count))

Output:

IP address IP-1 occured 1 times
IP address IP-4 occured 3 times
IP address IP-7 occured 1 times
IP address IP-2 occured 2 times 

You can also use map() to count the lines as well if you prefer:

ip_counts = Counter(map(str.strip, f))

Note: str.strip() is used here to strip whitespace from the keys, such as converting 'IP-1\n' to IP-1. This allows easier access to the keys in the future since you don't need to include whitespace.

If you want the maximum count, I would use max() with operator.itemgetter():

print(max(ip_counts.items(), key=itemgetter(1)))
# ('IP-4', 3)

Which returns the maximum tuple using the counts at index 1.

Multidimension array versus nested lists in python

Python does not have a multidimensional array type. It only has lists.

numpy (a 3rd-party Python extension) does have array types, and these serve a specialized function within that library, namely fast C-based mathematical operations on homogenous sequences.

With the standard Python list type, putting one inside the other creates a nested structure that can be used to model a multidimensional structure. You nest the [index] item access, [1][42] first retrieves the second element of the outer list, then the 43rd element of that second element.

numpy arrays are specialist structures that explicitly model multiple dimensions as part of the main type, rather than nesting arrays inside arrays, and that means they can support addressing of multiple dimensions in the [index] syntax, where index comes in the form of a tuple, technically.

Python does have a single dimensional array type, that, like numpy arrays, models homogenous C-type sequences.

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