Solving Perl Weekly Challenge 095 -- Palindrome Number and Stack
作者：gugod 發佈於： #rakuTwo basic tasks from Perl Weekly Challenge 095. Palindrome number is also on leetcode: leetcode/palindrome-number. For languages that coerce values to Int / Str automatically, these two tasks does not require too much code.
TASK #1 › Palindrome Number
Submitted by: Mohammad S Anwar
You are given a number $N.
Write a script to figure out if the given number is Palindrome. Print 1 if true otherwise 0.
Example 1:
Input: 1221
Output: 1
Example 2:
Input: -101
Output: 0, since -101 and 101- are not the same.
Example 3:
Input: 90
Output: 0
Solution #1 > Palindrome Number
It is pretty straightforward: simply convert the input number to string, then check whether that string is palindromic. Based on the example, all negative numbers are non-palindromic. I wonder numbers with decimal points are considered.
Let's say we are only dealing with integers. Here's the implementation in Raku.
sub is-palindrome-number (Int $n --> Bool) {
return "$n" eq "$n".flip;
}The operation of flipping a string corresponds to the flip subroutine from Str in Raku. To convert a number $n to string, either $n.Str or "$n" would do. The part where it says (Int $n --> Bool) is the signature of this subroutine. It means that the subroutine takes one Int argument, and returns a Bool (Boolean values. True or False.)
TASK #2 › Demo Stack
Submitted by: Mohammad S Anwar
Write a script to demonstrate Stack operations like below: push($n) - add $n to the stack pop() - remove the top element top() - get the top element min() - return the minimum element
Example:
my $stack = Stack->new;
$stack->push(2);
$stack->push(-1);
$stack->push(0);
$stack->pop; # removes 0
print $stack->top; # prints -1
$stack->push(0);
print $stack->min; # prints -1
Solution #2 > Demo Stack
If we are just defining a class with the abovementioned methods, they can all be delegated to one subroutine in Raku. Let's use this IntStack as an example, which is stack that can hold a bunch of integers.
class IntStack {
has Int @!store;
method push(Int $n) {
@!store.push($n);
}
method pop(--> Int) {
@!store.pop;
}
method top(--> Int) {
@!store.tail;
}
method min(--> Int) {
@!store.min;
}
}Which can be used like this:
my $stack = IntStack.new;
$stack.push(2);
$stack.push(-1);
$stack.push(0);
$stack.pop;
say $stack.top; #=> -1
$stack.push(0);
say $stack.min; #=> -1