Jagged array

Memory layout of a jagged array.

In computer science, a jagged array, also known as a ragged array ^[1] or irregular array ^[2] is an array of arrays of which the member arrays can be of different lengths, ^[3] producing rows of jagged edges when visualized as output. In contrast, two-dimensional arrays are always rectangular ^[4] so jagged arrays should not be confused with multidimensional arrays, but the former is often used to emulate the latter.

Arrays of arrays in languages such as Java, PHP, Python (multidimensional lists), Ruby, C#.NET, Visual Basic.NET, Perl, JavaScript, Objective-C, Swift, and Atlas Autocode are implemented as Iliffe vectors.

Examples

In C# and Java ^[5] jagged arrays can be created with the following code: ^[6]

int[][]c;c=newint[2][];// creates 2 rowsc[0]=newint[5];// 5 columns for row 0c[1]=newint[3];// create 3 columns for row 1

In C and C++, a jagged array can be created (on the stack) using the following code:

intjagged_row0[]={0,1};intjagged_row1[]={1,2,3};int*jagged[]={jagged_row0,jagged_row1};

In C/C++, jagged arrays can also be created (on the heap) with an array of pointers:

int*jagged[5];jagged[0]=malloc(sizeof(int)*10);jagged[1]=malloc(sizeof(int)*3);

In C++/CLI, jagged array can be created with the code: ^[7]

usingnamespaceSystem;intmain(){array<array<double>^>^Arrayname=gcnewarray<array<double>^>(4);// array contains 4 //elementsreturn0;}

In Fortran, a jagged array can be created using derived types with allocatable component(s):

type::Jagged_typeinteger,allocatable::row(:)end type Jagged_typetype(Jagged_type)::Jagged(3)Jagged(1)%row=[1]Jagged(2)%row=[1,2]Jagged(3)%row=[1,2,3]

In Python, jagged arrays are not native but one can use list comprehensions to create a multi-dimensional list which supports any dimensional matrix: ^[8]

multi_list_3d=[[[]foriinrange(3)]foriinrange(3)]# Produces: [[[], [], []], [[], [], []], [[], [], []]]multi_list_5d=[[[]foriinrange(5)]foriinrange(5)]# Produces: [[[], [], [], [], []], [[], [], [], [], []], [[], [], [], [], []], [[], [], [], [], []], [[], [], [], [], []]]

See also

• Variable-length array
• Iliffe vector

References

1. King, K. N. (2008). C Programming. W. W. Norton. p. 301. ISBN   978-0-393-97950-3.
2. Handbook of Data Structures and Applications. CRC Press. 2004.
3. Jesse Liberty; Brian MacDonald (18 November 2008). Learning C# 3.0. "O'Reilly Media, Inc.". pp. 210–. ISBN   978-0-596-55420-0.
4. Don Box (2002). Essential .Net: The Common Language Runtime. Addison-Wesley Professional. p. 138. ISBN   978-0-201-73411-9.
5. "Jagged Array in Java - GeeksforGeeks". GeeksforGeeks. 2016-02-03. Retrieved 2018-08-13.
6. Paul J. Deitel; Harvey M. Deitel (26 September 2008). C# 2008 for Programmers. Pearson Education. p. 40. ISBN   978-0-13-701188-9.
7. "Jagged Arrays". FunctionX. Retrieved 26 November 2014.
8. "Lists in Python Demystified". Alvin.io. Archived from the original on 15 October 2016. Retrieved 31 January 2016.