def editDistance(r, h):
    '''
    This function is to calculate the edit distance of reference sentence and the hypothesis sentence.

    Main algorithm used is dynamic programming.

    Attributes:
        r -> the list of words produced by splitting reference sentence.
        h -> the list of words produced by splitting hypothesis sentence.
    '''
    d = numpy.zeros((len(r)+1)*(len(h)+1), dtype=numpy.uint8).reshape((len(r)+1, len(h)+1))

    for i in range(len(r)+1):
        for j in range(len(h)+1):
            if i == 0:
                d[0][j] = j
            elif j == 0:
                d[i][0] = i

    for i in range(1, len(r)+1):
        for j in range(1, len(h)+1):
            if r[i-1] == h[j-1]:
                d[i][j] = d[i-1][j-1]
            else:
                substitute = d[i-1][j-1] + 1
                insert = d[i][j-1] + 1
                delete = d[i-1][j] + 1
                d[i][j] = min(substitute, insert, delete)
    return d