How to resolve the algorithm Look-and-say sequence step by step in the ALGOL-M programming language

Published on 12 May 2024 09:40 PM
#Algol-m

How to resolve the algorithm Look-and-say sequence step by step in the ALGOL-M programming language

Table of Contents

Problem Statement

The   Look and say sequence   is a recursively defined sequence of numbers studied most notably by   John Conway.

The   look-and-say sequence   is also known as the   Morris Number Sequence,   after cryptographer Robert Morris,   and the puzzle   What is the next number in the sequence 1,   11,   21,   1211,   111221?   is sometimes referred to as the Cuckoo's Egg,   from a description of Morris in Clifford Stoll's book   The Cuckoo's Egg.

Sequence Definition

An example:

Write a program to generate successive members of the look-and-say sequence.

Let's start with the solution:

Step by Step solution about How to resolve the algorithm Look-and-say sequence step by step in the ALGOL-M programming language

Source code in the algol-m programming language

begin
    string(1) function digit(n);
    integer n;
    case n of begin
        digit := "0";   digit := "1";   digit := "2";
        digit := "3";   digit := "4";   digit := "5";
        digit := "6";   digit := "7";   digit := "8";
        digit := "9";
    end;
    
    string(1) array cur[1:128];
    string(1) array next[1:128];
    integer curlen, i, cnt, j, n;
    
    cur[1] := "1";
    curlen := 1;
    
    for n := 1 step 1 until 15 do begin
        write("");
        for i := 1 step 1 until curlen do 
            writeon(cur[i]);
        
        i := j := 1;
        while i <= curlen do begin
            cnt := 1;
            while cur[i + cnt] = cur[i] do 
                cnt := cnt + 1;
            next[j] := digit(cnt);
            next[j + 1] := cur[i];
            j := j + 2;
            i := i + cnt;
        end;
        
        for i := 1 step 1 until j-1 do
            cur[i] := next[i];
        
        curlen := j - 1;
    end;
end

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