Tag Archives: Array

Java, Lists, PHP, Python

Check if object is in (multidimensional) array?

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Python:

>>> arr = [[1,3],[2,4]]
>>> 2 in [x[0] for x in arr]
True
>>> 3 in [x[0] for x in arr]
False

PHP:

$arr = [[1,3],[2,4]];
var_dump(in_array(1, array_map(function($x){return $x[0];},$arr), true));
var_dump(in_array(3, array_map(function($x){return $x[0];},$arr), true));

Gives

bool(true)
bool(false)

Adding true for “strict mode”, to prevent false positives (1 == true, 0 == false)

Java:

int[][] arr = {{1,3},{2,4}};
System.out.println(Arrays.stream(arr).map(x -> x[0]).collect(Collectors.toList()).contains(1));
System.out.println(Arrays.stream(arr).map(x -> x[0]).collect(Collectors.toList()).contains(3));

Gives

true
false

Java, Lists, PHP, Python

Converting arrays to/from strings

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Found myself using these functions in various prints to interfaces and whatnot, so here’s the elegant ways of creating comma-separated strings. The added bonus is that this method allows for separation of data in for-loops. Early on I’d usually add a separation manually in each step of the loop and finish by removing the extra separation at the end.

Python:

string = ",".join(['1','2','3','4'])
array = string.split(",")

PHP:

echo($str = implode(",", [1,2,3,4,5]));
var_dump(explode(",",$str));

Java:

With Apache Commons:

StringUtils.join(new String[]{"1","2","3"}, ',');

In Android:

TextUtils.join(new String[]{"1","2","3"}, ',');

Without requires a bit of setup with StringBuilder and a for-loop, unless you use JDK8:

String[] array = {"1", "2", "3", "4", "5"};
System.out.println(String.join(",",array));

Check out the new StringJoiner class for some interesting helper functions.