Longest Palindromic Substring in COBOL

Longest Palindromic

Substring in COBOL

Welcome to the Longest Palindromic Substring in COBOL page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

identification division.
program-id. longest-palindromic-substring.

data division.
working-storage section.

01 ws-s              pic x(200).
01 ws-len            pic 9(4).

01 ws-i              pic 9(4).
01 ws-l              pic 9(4).
01 ws-r              pic 9(4).

01 ws-best-l         pic 9(4) value 0.
01 ws-best-r         pic 9(4) value 0.
01 ws-best-len       pic 9(4) value 0.
01 ws-r-len          pic 9(4) value 0.

01 ws-valid          pic x value "y".
   88 is-valid       value "y".
   88 is-invalid      value "n".

procedure division.

main.
    accept ws-s from argument-value

    if ws-s = spaces
        perform show-usage
        stop run
    end-if

    move function length(function trim(ws-s)) to ws-len

    if ws-len = 0
        perform show-usage
        stop run
    end-if

    perform find-palindrome

    if ws-best-len < 2
        perform show-usage
        stop run
    end-if

    perform varying ws-i from ws-best-l by 1 until ws-i > ws-best-r
        display ws-s(ws-i:1) with no advancing
    end-perform
    stop run.

find-palindrome.
    perform varying ws-i from 1 by 1 until ws-i > ws-len

        move ws-i to ws-l
        move ws-i to ws-r

        perform expand

        move ws-i to ws-l
        compute ws-r = ws-i + 1

        perform expand

    end-perform.

expand.
    perform until ws-l < 1 or ws-r > ws-len
        if ws-s(ws-l:1) not = ws-s(ws-r:1)
            exit perform
        end-if

        compute ws-l = ws-l - 1
        compute ws-r = ws-r + 1
    end-perform

    compute ws-l = ws-l + 1
    compute ws-r = ws-r - 1

    compute ws-r-len = ws-r - ws-l + 1

    if ws-r-len > ws-best-len
        move ws-r-len to ws-best-len
        move ws-l to ws-best-l
        move ws-r to ws-best-r
    end-if.

show-usage.
    display "Usage: please provide a string that contains at least one palindrome".

Longest Palindromic Substring in COBOL was written by:

• Ștefan-Iulian Alecu

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

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How to Run the Solution

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