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Min Coin Change

Hi Experts,

I am trying to solve the min coin change problem in SAP ABAP . I would have to create a matrix table dynamically. I have searched the SCN and found few posts, But everything is about creating a field catalog. Creating a matrix using "For" constructor creates a deep structure.

Is there a simple way to create a dynamic matrix table in ABAP?

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  • You say "Creating a matrix using "For" constructor creates a deep structure."

    If "deep structure" is the official ABAP term (see Glossary - Deep), you're wrong. It may create a "flat" or "deep" structure i.e. any kind of structure...

    What can be said, but it has no importance concerning your question, is that "For" creates a structure based on a standalone and complete/non-generic data type (see ABAP documentations Glossary - Standalone data type and Glossary - complete data type).

    What you are looking for is Run Time Type Creation (see ABAP documentation Glossary - Run Time Type Creation).

  • Hi,

    Thanks for explaining the differences and that "For" constructor is easier to use than actually creating Run time type creation. "For" matrix creation is clearly easily accessible.

  • Additional remarks about the wording. As I re-read my last comment, ""For" constructor creates a [...] structure" shocked me so I want to clarify my last comment.

    "For" is not a constructor (operator?), only "value", "reduce" and so on are constructor operators. Eventually "for" is a possible element of a constructor expression. It's more precise to say that "For" is a loop over an internal table(s) to append or initialize another internal table or to reduce it to any kind of data object.

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  • Best Answer
    Posted on Jul 03 at 10:48 PM


    As suggested I used "For" over "Value" to create a matrix to solve the problem. Used the sample code from

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  • Posted on Jun 30 at 10:51 PM

    I personally would prefer using a matrix with a deep structure (table in table), but you certainly can also create a table type with the amount of necessary columns dynamically.

    • First of all you have to give your columns field names and they cant start with a number so either a letter or underscore '_x' would be an option.
    • And especially accessing this table is not as neat:
      ASSIGN COMPONENT y OF STRUCTURE <table>[ x ] TO <fs>.
      ASSIGN <table>[ x ][ y ] TO <fs>.
    • Also, the matrix with a table in table can be 'easily' enlarged or shortened, whereas the matrix with a fixed structure needs to be recreated
    • If you have hoped for something other than a solution of a table with fixed fields or a table in table, I currently have to disappoint you, but I am also not sure what exactly you are looking for instead.

    But this would be a sample coding to do the job. It is probably not as 'simple' as you would have hoped for, but it still might be shortened in one way or the other. Both logics, matrix with table in table and table with struc are presented in this coding:

    REPORT zdemo_matrix.
        CLASS-METHODS: main.
          rows    TYPE i,
          columns TYPE i,
          x       TYPE i VALUE 1,
          y       TYPE i VALUE 1.
        CLASS-METHODS initialize.
      METHOD main.
        initialize( ).
    * create the matrix based on table in table
               t_rows   TYPE STANDARD TABLE OF t_column WITH EMPTY KEY.
        DATA(matrix_tab) = VALUE t_rows(
            FOR i = 0 UNTIL i > columns - 1 (
              VALUE t_column(
                FOR j = 1 UNTIL j > rows
                  ( sy-abcde+i(1) && |{ j }| ) ) ) ).
    * matrix based on table in table created
    * create the matrix based on table with structure
        DATA abaptype  TYPE REF TO cl_abap_datadescr.
        DATA row       TYPE int4.
        DATA column    TYPE int4.
        DATA dref      TYPE REF TO data.
        abaptype ?= cl_abap_datadescr=>describe_by_name( 'STRING' ). " cell type definition
        DATA(comp_tab) = VALUE abap_component_tab( FOR i = 0 UNTIL i >= columns " create row components based on cell
                         ( name = sy-abcde+i(1) type = abaptype ) ). " opted for single letters as column name
                                                                     " with current limit of 26 columns
        DATA(structype) = cl_abap_structdescr=>create( comp_tab ). " create row structure
        DATA(tabletype) = cl_abap_tabledescr=>create( " create table based on row structure
                          p_line_type = structype p_table_kind = 'S' ).
        CREATE DATA dref TYPE HANDLE tabletype.
        ASSIGN dref->* TO <matrix_str>. " the matrix table (without rows yet)
        DO rows TIMES. " creating rows for matrix with columns
          row = row + 1.
          APPEND INITIAL LINE TO <matrix_str> ASSIGNING FIELD-SYMBOL(<line>). 
          DO columns TIMES. " creating inital xy-values
            column = sy-index - 1.
            ASSIGN COMPONENT sy-index OF STRUCTURE <line> TO FIELD-SYMBOL(<fs>).
            <fs> = sy-abcde+column(1) && |{ row }|.
    * matrix based on table with structure created
    * Access & display matrix as table in table
        ASSIGN matrix_tab[ x ][ y ] TO <fs>. " access matrix-cell of table in table
        cl_demo_output=>write_data( <fs> ).
        cl_demo_output=>write_data( matrix_tab ).
    * Access & display matrix as table with struc 
        ASSIGN COMPONENT y OF STRUCTURE <matrix_str>[ x ] TO <fs>. " access matrix-cell of table with structure
        cl_demo_output=>write_data( <fs> ).
        cl_demo_output=>write_data( <matrix_str> ).
        cl_demo_output=>display( ).
      METHOD initialize.
        rows = 100.
        columns = strlen( sy-abcde ).
        cl_demo_input=>add_field( CHANGING field = x ).
        cl_demo_input=>add_field( CHANGING field = y ).
        cl_demo_input=>request( ).
      demo=>main( ).

    matrix-demo.png (235.7 kB)
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