Idiom #240 Sort 2 lists together

Lists a and b have the same length. Apply the same permutation to a and b to have them sorted based on the values of a.

Idiom #353 Test if list is sorted

Set the boolean b to true if the list items has all its elements in increasing order, false otherwise.

The order is not strict: the ordered list may contain duplicate elements.

Idiom #124 Binary search for a value in sorted array

Write the function binarySearch which returns the index of an element having the value x in the sorted array a, or -1 if no such element exists.

Idiom #28 Sort by a property

Sort the elements of the list (or array-like collection) items in ascending order of x.p, where p is a field of the type Item of the objects in items.

Idiom #290 Sort sublist

Sort the part of the list items from index i (included) to index j (excluded), in place, using the comparator c.

Elements before i and after j must remain unchanged.

Idiom #297 Sort a list of strings, case-insensitively

Sort the string list data in a case-insensitive manner.

The sorting must not destroy the original casing of the strings.

Idiom #100 Sort by a comparator

Sort elements of array-like collection items, using a comparator c.

Idiom #108 Determine if variable name is defined

Print the value of variable x, but only if x has been declared in this program.
This makes sense in some languages, not all of them. (Null values are not the point, rather the very existence of the variable.)

Idiom #65 Format decimal number

From the real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 -> "15.6%"

Idiom #282 Use a custom type as map key

Declare a type Foo, and create a new map with Foo as key type.

Mention the conditions on Foo required to make it a possible map key type.

Idiom #119 Deduplicate list

Remove duplicates from the list x.
Explain if the original order is preserved.

Idiom #113 Iterate over map entries, ordered by values

Print each key k with its value x from an associative array mymap, in ascending order of x.
Multiple entries may exist for the same value x.

Idiom #13 Iterate over map keys and values

Access each key k with its value x from an associative array mymap, and print them.

Traversing each key and each associated object of mymap

Idiom #112 Iterate over map entries, ordered by keys

Print each key k with its value x from an associative array mymap, in ascending order of k.

Idiom #246 Count distinct elements

Set c to the number of distinct elements in the list items.

Idiom #10 Shuffle a list

Generate a random permutation of the elements of list x

Idiom #3 Create a procedure

Like a function which doesn't return any value, thus has only side effects (e.g. Print to standard output)

Idiom #12 Check if list contains a value

Check if the list contains the value x.
list is an iterable finite container.

Idiom #187 Disjoint Set

Disjoint Sets hold elements that are partitioned into a number of disjoint (non-overlapping) sets.