  The ground state phase diagram of two-dimensional electrons in high magnetic
field is studied by the density matrix renormalization group (DMRG) method. The
low energy excitations and pair correlation functions in Landau levels of
N=0,1,2 are calculated for wide range of fillings. The obtained results for
systems with up to 25 electrons confirm the existence of various electronic
states in quantum Hall systems. The ground state phase diagram for N=0,1,2
consisting of incompressible liquids, compressible liquids, charge density
waves called stripe, bubble and Wigner crystal is determined.
