How to resolve the algorithm Count occurrences of a substring step by step in the Erlang programming language

Published on 12 May 2024 09:40 PM
#Erlang

How to resolve the algorithm Count occurrences of a substring step by step in the Erlang programming language

Table of Contents

Problem Statement

Create a function,   or show a built-in function,   to count the number of non-overlapping occurrences of a substring inside a string. The function should take two arguments:

It should return an integer count. The matching should yield the highest number of non-overlapping matches. In general, this essentially means matching from left-to-right or right-to-left   (see proof on talk page).

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Count occurrences of a substring step by step in the Erlang programming language

Source code in the erlang programming language

%% Count non-overlapping substrings in Erlang for the rosetta code wiki.
%% Implemented by J.W. Luiten

-module(substrings).
-export([main/2]).

%% String and Sub exhausted, count a match and present result
match([], [], _OrigSub, Acc) ->
  Acc+1;

%% String exhausted, present result
match([], _Sub, _OrigSub, Acc) ->
  Acc;
	
%% Sub exhausted, count a match
match(String, [], Sub, Acc) ->
  match(String, Sub, Sub, Acc+1);

%% First character matches, advance
match([X|MainTail], [X|SubTail], Sub, Acc) ->
  match(MainTail, SubTail, Sub, Acc);

%% First characters do not match. Keep scanning for sub in remainder of string
match([_X|MainTail], [_Y|_SubTail], Sub, Acc)->
  match(MainTail, Sub, Sub, Acc).
	
main(String, Sub) ->
   match(String, Sub, Sub, 0).


substrings:main("ababababab","abab").


main( String, Sub ) -> erlang:length( binary:split(binary:list_to_bin(String), binary:list_to_bin(Sub), [global]) ) - 1.

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