Sparse Table | Java program to do range minimum query using sparse table ; lookup [ i ] [ j ] is going to store minimum value in arr [ i . . j ] . Ideally lookup table size should not be fixed and should be determined using n Log n . It is kept constant to keep code simple . ; Fills lookup array lookup [ ] [ ] in bottom up manner . ; Initialize M for the intervals with length 1 ; Compute values from smaller to bigger intervals ; Compute minimum value for all intervals with size 2 ^ j ; For arr [ 2 ] [ 10 ] , we compare arr [ lookup [ 0 ] [ 7 ] ] and arr [ lookup [ 3 ] [ 10 ] ] ; Returns minimum of arr [ L . . R ] ; Find highest power of 2 that is smaller than or equal to count of elements in given range . For [ 2 , 10 ] , j = 3 ; 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 ] ] , ; Driver program
import java . io . * ; class GFG { static int MAX = 500 ; static int [ ] [ ] lookup = new int [ MAX ] [ MAX ] ; static void buildSparseTable ( int arr [ ] , int n ) { for ( int i = 0 ; i < n ; i ++ ) lookup [ i ] [ 0 ] = arr [ i ] ; for ( int j = 1 ; ( 1 << j ) <= n ; j ++ ) { for ( int i = 0 ; ( i + ( 1 << j ) - 1 ) < n ; i ++ ) { if ( lookup [ i ] [ j - 1 ] < lookup [ i + ( 1 << ( j - 1 ) ) ] [ j - 1 ] ) lookup [ i ] [ j ] = lookup [ i ] [ j - 1 ] ; else lookup [ i ] [ j ] = lookup [ i + ( 1 << ( j - 1 ) ) ] [ j - 1 ] ; } } } static int query ( int L , int R ) { int j = ( int ) Math . log ( R - L + 1 ) ; if ( lookup [ L ] [ j ] <= lookup [ R - ( 1 << j ) + 1 ] [ j ] ) return lookup [ L ] [ j ] ; else return lookup [ R - ( 1 << j ) + 1 ] [ j ] ; } public static void main ( String [ ] args ) { int a [ ] = { 7 , 2 , 3 , 0 , 5 , 10 , 3 , 12 , 18 } ; int n = a . length ; buildSparseTable ( a , n ) ; System . out . println ( query ( 0 , 4 ) ) ; System . out . println ( query ( 4 , 7 ) ) ; System . out . println ( query ( 7 , 8 ) ) ; } }