Shell Programming and Scripting

1,2
2,4
3,6
4,9
9,10

1,10
2,10
3,6
4,1
9,10

1,10
2,10
3,6
4,10
9,10

1--->2--->4-->9---->10

#!/usr/bin/perl
open I,$ARGV[0];
while (<I>){
  chomp;
  @x=split /,/;
  $a{$x[0]}=$x[1];
}
for $i (keys %a){
  $t=$a{$i};
  $b{$i}=$a{$i};
  $q=1;
  while ($q){
    if ($a{$t}){
      $q=1;
      $b{$i}=$a{$t};
      $t=$a{$t};
    } else {
      $q=0;
    }
  }
}
for $i (keys %b){
  print "$i,$b{$i}\n";
}

 awk -F , '
    BEGIN { max = 0; }
    {
        nxt[$1+0] = $2+0;
        if( $1+0 > max )
            max = $1;
        next;
    }
    END {
        for( i = 1; i <= max; i++ )
        {
            if( nxt[i] != "" )
            {
                n = i;
                while( nxt[n] != "" )
                    n = nxt[n];
                printf( "%d,%d\n", i, n );
            }
        }
    }
'  input-file

 awk -F , '
    { nxt[$1+0] = $2+0; }
    END {
        for( i in nxt )
        {
                n = i;
                while( n in nxt )
                    n = nxt[n];
                printf( "%d,%d\n", i, n );
        }
    }
' input-file

awk -F , 'FNR==NR {nxt[$1+0]=$2+0;next}
{for(n=$1;n in nxt;n=nxt[n]); print $1","n}' infile infile