def determine_rg_type(strand1, strand2, chr1, chr2):
    """Determine the rgtype for strand information."""
    if chr1 != chr2:
        return 'translocation'
    elif strand1 != strand2:
        return 'inversion'
    elif strand1 == "+" and strand2 == "+":
        return 'deletion'
    elif strand1 == "-" and strand2 == "-":
        return 'tandem_dup'