Collect tiles that can decrease the xiangting number of hands if they are drawn. In case there are no tingpais for the hand, the function warns about it and returns an empty character vector.
collect_tingpai(pai)
A list of character vectors.
collect_tingpai(c("m345567p234s3378", "p222345z1234567"))
#> [[1]]
#> [1] "s6" "s9"
#>
#> [[2]]
#> [1] "z1" "z2" "z3" "z4" "z5" "z6" "z7"
#>