find value of rows having first column value equal to zero
for ( int i = 0 ; i < n ; ++ i ) { if ( A [ i ] [ 0 ] == 0 ) { int ans = 0 ; for ( int j = 1 ; j < m ; ++ j ) ans = ( int ) ( ans + A [ i ] [ j ] * Math . pow ( 2 , m - j - 1 ) ) ; update . put ( ans , i ) ; } }