Jagged Arrays in C++ – GeeksforGeeks

Prerequisite: 

What is a Jagged Array?

A jagged array is an array of arrays such that member arrays can be of different sizes, in 2D array terms for each row we can have a variable number of columns. These types of arrays are also known as Jagged arrays. 

Jagged Array in C++

Example:

arr[3][] = 1 2 3 4        // arr[0][4] : 1st row have 4 columns
           5 6            // arr[1][2] : 2nd row have 2 columns
           7 8 9          // arr[2][3] : 3rd row have 3 columns

Methods to Create Jagged Array

Jagged Array can be implemented in C++ in two ways:

1. Using a static array of pointers
2. Using dynamic 2D arrays

1. Using a static array of pointers

• create ‘n’ numbers 1D-arrays (row1, row2, row3, ….. etc.) where n is no of rows, the size of each row array will be No. of columns i.e, the number of elements in each row array will show no. of columns in that particular row.
• Create a 1D array of pointers, storing the base address of each row array.
• Create another 1D array Sizes[] storing the size of each row array (This helps while iterating each element).

To know about the array of pointers refer to an array of pointers article.

Below is the implementation of the above method:

elements in matrix form as follow
1 2 3 4 
5 6 
7 8 9 

2. Using Dynamic 2D arrays

• Create row, col variables storing no. of rows and no. of columns.
• Create a Dynamic row array arr (array of pointers) that can store a “row” number of addresses.
• Store size in another 1D array Sizes[] (size of no. or Rows) to store no. of columns for each row element in the row array. (This helps while iterating each column for each row).
• Create a Dynamic Column array for each row element with size: sizes[i]  
• Now each row element in the Row array has the Base address of each Column array.

Below is the implementation of the above method:

elements in matrix form as follow
1 2 3 4 
5 6 
7 8 9