Find the number of 5 digit numbers that contain four 5s-CodePudding

I want to find 5 digit numbers that have four 5s. I do the following:

data <- str_split(as.character(x = 10000:99999), pattern = "")

but when I try to find the number of lists that contain four 5s

sapply(data, function(x) c("5", "5", "5", "5") %in% data[[x]]) it gives me an error "Error in data[[x]] : no such index at level 1":

What am I doing wrong? any other more elegant solution?

CodePudding user response：

Try this?

> x <- 10000:99999

> x[nchar(gsub("[^5]", "", x)) == 4 & nchar(x)==5]
 [1] 15555 25555 35555 45555 50555 51555 52555 53555 54555 55055 55155 55255
[13] 55355 55455 55505 55515 55525 55535 55545 55550 55551 55552 55553 55554
[25] 55556 55557 55558 55559 55565 55575 55585 55595 55655 55755 55855 55955
[37] 56555 57555 58555 59555 65555 75555 85555 95555

Or, you can generalize it like below

# number of digits
n <- 5 
# number of 5s
m <- 4
# output
(x <- 10^(n - 1):(10^n - 1))[nchar(gsub("[^5]", "", x)) == m]

CodePudding user response：

grep('^(?=.{5}$).*?(5)(.*?\\1){3}', 10000:99999, value = TRUE, perl=TRUE)

 [1] "15555" "25555" "35555" "45555" "50555" "51555" "52555" "53555"
 [9] "54555" "55055" "55155" "55255" "55355" "55455" "55505" "55515"
[17] "55525" "55535" "55545" "55550" "55551" "55552" "55553" "55554"
[25] "55555" "55556" "55557" "55558" "55559" "55565" "55575" "55585"
[33] "55595" "55655" "55755" "55855" "55955" "56555" "57555" "58555"
[41] "59555" "65555" "75555" "85555" "95555"

Regex Explanation:

Use a lookahead to determine whether the number contains five digits. ie ^(?=.{5}$). Then determine whethere there are 4 5's .*?(5)(.*?\\1){3}

CodePudding user response：

This would be one way:

library(dplyr)
library(tibble)
enframe(10000:99999) %>% 
    mutate(
        name = 10000:99999,
        value = as.character(value),
        value = str_split(value, '')
    ) %>% 
    unnest(value) %>% 
    filter(value == 5) %>% 
    count(name) %>% 
    filter(n == 4) %>%
    select(-n)
# A tibble: 44 x 1
    name
   <int>
 1 15555
 2 25555
 3 35555
 4 45555
 5 50555
 6 51555
 7 52555
 8 53555
 9 54555
10 55055
# ... with 34 more rows

CodePudding user response：

I think the simplest is

5*9-1
# 44

This works because out of the five digits, exactly one is not five (leaving four fives remaining). For each non-five digit it can take any one of 9 different values (i.e. 0 to 9, except 5). Then we subtract 1 because we don't allow 05555, which would be a four digit number.

CodePudding user response：

Would this be an alternative? Not sure if you explicitly need characters.

EDIT: Question states "has 4 5s", but not if exclusively. 55555 also has 4 5s. So giving both solutions here.

If 4 5s

c(10000:99999)[grep("5.555|55.55|555.5|5555", 10000:99999 )]

 [1] 15555 25555 35555 45555 50555 51555 52555 53555 54555 55055 55155 55255
[13] 55355 55455 55505 55515 55525 55535 55545 55550 55551 55552 55553 55554
[25] 55555 55556 55557 55558 55559 55565 55575 55585 55595 55655 55755 55855
[37] 55955 56555 57555 58555 59555 65555 75555 85555 95555

If only 4 5s

c(10000:99999)[grep("5[^5]555|55[^5]55|555[^5]5|[^5]5555|5555[^5]",c(10000:99999)) ]

 [1] 15555 25555 35555 45555 50555 51555 52555 53555 54555 55055 55155 55255
[13] 55355 55455 55505 55515 55525 55535 55545 55550 55551 55552 55553 55554
[25] 55556 55557 55558 55559 55565 55575 55585 55595 55655 55755 55855 55955
[37] 56555 57555 58555 59555 65555 75555 85555 95555

CodePudding user response：

This should get you started. It will extract all the 5's from an expression and then count them. Add na logic.

 library(stringr)
 y <- nchar(str_extract(data, "[5] " ))  = 4