Compute minimum of last 2 ^ j elements with first 2 ^ j elements in range . For [ 2 , 10 ] , we compare arr [ lookup [ 0 ] [ 3 ] ] and arr [ lookup [ 3 ] [ 3 ] ] ,
if ( lookup [ L ] [ j ] <= lookup [ R - ( 1 << j ) + 1 ] [ j ] ) return lookup [ L ] [ j ] ; else return lookup [ R - ( 1 << j ) + 1 ] [ j ] ; }