Hello.

I used regex to solve one problem in contest. And received error message. Later I can't understand my mistake, how I have got it.

The problem. You are given an array of non-decreasing elements. Your task is to find (if any) two rightmost neighbouring elements whose difference is bigger than some number (c) and delete left element and all preceding elements. Then say how much elements have left.

It seems that simple procedural programming here is suitable much more than regex. But I tried with regex:

#!/usr/bin/perl

use warnings;
use strict;

while(my $c = <>){
    $_ = <>;
    s/
    .*?(\b\d+)[ ]
    (?=(\d+)\b)
    (??{
        print "[$1 $2]\n";
        $2 - $1 <= $c ? 'X' : ''
    })
    /
    (print "DELETED:[$&] REMAINS:[$']\n"),
    ''
    /egx;
    printf "NUMBERS:[%d:%s]\n", (length s/\d//gr), $_;
    print '-' x 10, "\n";
    }

[download]
INPUT: 
1
1000000000
5
1 1 1 2 2 2
1
1 3 5 7 9 10
1
1 2 3 4
5
28 31 36 43
5
1 3 8 14 19 26 33
1
1 2 3 4

[download]
OUTPUT: 
NUMBERS:[1:1000000000
]
----------
[1 1]
[1 1]
[1 2]
[2 2]
[2 2]
[1 1]
[1 2]
[2 2]
[2 2]
[1 1]
[1 2]
[2 2]
[2 2]
[1 2]
[2 2]
[2 2]
[1 2]
[2 2]
[2 2]
[2 2]
[2 2]
[2 2]
[2 2]
[2 2]
[2 2]
NUMBERS:[6:1 1 1 2 2 2
]
----------
[1 3]
DELETED:[1 ] REMAINS:[3 5 7 9 10
]
[3 5]
DELETED:[3 ] REMAINS:[5 7 9 10
]
[5 7]
DELETED:[5 ] REMAINS:[7 9 10
]
[7 9]
DELETED:[7 ] REMAINS:[9 10
]
[9 10]
NUMBERS:[2:9 10
]
----------
[1 2]
[2 3]
[3 4]
[2 3]
[3 4]
[2 3]
[3 4]
[3 4]
[3 4]
NUMBERS:[4:1 2 3 4
]
----------
[28 31]
[31 36]
[36 43]
DELETED:[28 31 36 ] REMAINS:[43
]
NUMBERS:[1:43
]
----------
[1 3]
[3 8]
[8 14]
DELETED:[1 3 8 ] REMAINS:[14 19 26 33
]
[14 19]
[19 26]
DELETED:[14 19 ] REMAINS:[26 33
]
Can't coerce UNKNOWN to string in substitution iterator at ./coerce.pl
+ line 11, <> line 12.

[download]

In reply to Can't coerce UNKNOWN to string in substitution iterator by rsFalse

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