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| -rw-r--r-- | challenge-194/james-smith/README.md | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/challenge-194/james-smith/README.md b/challenge-194/james-smith/README.md index 105067118c..5480e2db42 100644 --- a/challenge-194/james-smith/README.md +++ b/challenge-194/james-smith/README.md @@ -20,13 +20,21 @@ https://github.com/drbaggy/perlweeklychallenge-club/tree/master/challenge-193/ja ***You are given time in the format `hh:mm` with one missing digit. Write a script to find the highest digit between `0`-`9` that makes it valid time.*** ## Solution +Both solutions today use an ***IIFE*** (Immediately Invoked Function Expression) pronounced *iffy*. To remove the need for temporary variables. Each takes as input the result of an array method, here `split` and in the 2nd task `sort`. + +In this case we split the parameter into it's consitutant characters - the hours being in `0` & `1` and the minutes in `3` and `4`. Using a series of ternary operators we work out which position the "`?`" is in and work out what is the best digit for this place. + +If the "`?`" is in one of the minute slots this is easy as the value is either `5` or `9`. + +If it is in the hour slot we have to make sure the hour is less than 24. So if "`?`" is the first digit, we know that that can be a `2` only if the second digit is less than `4` and if it is in the second digit then the digit can only be `0` - `3` if the 1st digit is `2`. ```perl sub digit_2359 { sub { $_[0] eq '?' ? ( $_[1]<4 ? 2 : 1 ) : $_[1] eq '?' ? ( $_[0]<2 ? 9 : 3 ) - : $_[3] eq '?' ? 5 : 9 + : $_[3] eq '?' ? 5 + : 9 }->( split //, $_[0] ); } ``` @@ -38,7 +46,8 @@ sub digit_2400 { sub { $_[0] eq '?' ? ( $_[1]==4 && $_[3]==0 && $_[4]==0 || $_[1]<4 ? 2 : 1 ) : $_[1] eq '?' ? ( $_[0]<2 ? 9 : $_[3]==0 && $_[4]==0 ? 4 : 3 ) - : $_[3] eq '?' ? 5 : 9 + : $_[3] eq '?' ? 5 + : 9 }->( split //, $_[0] ); } ``` @@ -49,6 +58,12 @@ sub digit_2400 { ## Solution +Again we use and IIFE. This time taking the value of the sorted values from `%sc`. For the method to be true. The sorted values must be: + + * `n`, `n`, `n`, ...., `n`, `n+1` + +So we just need to check the 1st with the (n-1)st and the (n-1)st with the last! + ```perl sub check { my %sc; $sc{$_} ++ for split //,$_[0]; |