Shell Programming and Scripting

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R2 1 3
R3 2 4
R4 3 4
R5 5 6
R6 8 1
R7 6 7
R8 9 10

R1 1 2 3 4 8
R5 5 6 7
R8 9 10

awk  'NR==FNR{a[$2]=$3 ; a[$3]=$2;next} $2" "$3 in a {  print $1,a[$2" "$3]}'  file file

awk '
  $2 in A {
    A[$3]=A[$2]
    next
  } 
  $3 in A {
    A[$2]=A[$3]
    next
  }
  {
    A[$2]=A[$3]=$1
  }
  END {
    for(i in A) B[A[i]]=B[A[i]] i FS
    for(i in B) print i, B[i]
  }
' file

R1 2 3 4 8 1 
R5 5 6 7 
R8 9 10

awk '
  $2 in A {
    o=A[$3];
    for(i in A) if (A[i]==o) A[i]=A[$2]
    next
  } 
  $3 in A {
    A[$2]=A[$3]
    next
  }
  {
    A[$2]=A[$3]=$1
  }
  END {
    for(i in A) B[A[i]]=B[A[i]] i FS
    for(i in B) print i, B[i]
  }
' file