Merge a and b using rank compression
if ( r1 != r2 ) { if ( Rank [ r1 ] > Rank [ r2 ] ) { parent [ r2 ] = r1 ; Rank [ r1 ] += Rank [ r2 ] ; } else { parent [ r1 ] = r2 ; Rank [ r2 ] += Rank [ r1 ] ; } } }