Question

我希望通过使用数组和数组顶部编写代码来实现perl函数的push和pop功能。
例如：pop将弹出最后一个元素。但是如何通过获取数组的最后一个值来实现呢？

我写了下面的代码，但似乎不起作用。

#!/usr/bin/perl 
$in = $1; 
sub push { 
    my $top = 0; 
    @stack=("a","b","c"); 
    my $max = 20; 
    print "Push: @stack."; 
    if($top = $max - 1) { 
        print "Overflow"; 
    } 
    else { 
        $stack[$top] = $in; 
        $top = $top + 1; 
        print "After Push: @stack."; 
    } 
    print "Before Pop: @stack."; 
    my $new=$stack[$top]; 
    $top = $top - 1; 
    print "Popped item: $new."; 
    print "After Pop: @stack."; 
}

Answer 1

你没有说你想做什么，所以我们不能告诉你你是否这样做。但看起来您写的内容可以使用push和pop更清晰地写出来。

my $stack_size = 20;
my @stack;

sub push_onto_stack {
   my ($item) = @_;
   die "Overflow\n" if @stack > $stack_size;
   push @stack, $item;   
}

sub pop_from_stack {
   die "Stack empty\n" if !@stack;
   return pop @stack;
}

如果这是一项要求避免使用push和pop的作业，那么您可以使用

$stack[@stack] = $item;               # push @stack, $item

和

my $item = $stack[-1];  --$#stack;    # my $item = pop @stack;

Answer 2

我编写的代码如下：

#!/usr/bin/perl
use strict;
use warnings;

our @stack=("this","is","a","basic","example");
our $top = $#stack;

sub push_test {
    my $max = 7;
    print "\nCurrent Stack is: @stack\n";
    if($top == $max - 1)
    {
            print "\nScript Overflown. Testing others.\n";
    }
    else
    {
            $stack[@stack] = $in;
            $top+=1;
            print "After Push Stack is: @stack\n";
    }
}

sub pop_test {
    print "\nBefore Pop Stack is: @stack.\n";
    my $new = $stack[-1];
    --$#stack;
    print "Poped item is: $new.\n";
    print "After Pop Stack is: @stack\n";
}

sub peek_test {
    my $peek = $stack[0];
    print "\nPeek element is: $peek\n";
}

sub empty_test {
    print "\nTop value: $top.\n";
    if ($top == -1)
    {
    print "Array is empty.\n";
    }
    else
    {
    print "Array is not empty.\n";
    }
}

foreach $i (@ARGV){
    $in=$i;
    print "\nTESTING SCRIPT";
    print "\nTest: Push";
    push_test($in);
}
    print "\nTest: Pop";
    pop_test();
    print "\nTest: Peek";
    peek_test();
    print "\nTest: Is_empty";
    empty_test();
exit;

perl中的push和pop代码？

2 个答案: