Perl |实现堆栈
Perl 中的堆栈是一种线性数据结构，遵循后进先出(后进先出)或 FILO (先进后出)的顺序。 简单来说，栈是一个数组，其中插入和删除只发生在称为栈顶的一端。 推是将元素插入堆栈的过程。 弹出是移除堆栈最顶层元素的过程。
Making a stack
用 Perl 创建堆栈相当简单。我们只需要声明一个数组。 堆栈可以是空的，如下所示:
@stack;
或者它可以被初始化:
@stack = (1, 2, 3);
Pushing items to a stack
可以使用推送()功能或拼接()功能进行推送。
- 使用推送()推送:
语法:推送(@stack，list)； T3】参数:
- @ stack–要在其上执行推送的堆栈。
- 列表–要推入堆栈的元素。这些元素可以是标量、数组、散列或它们的任意组合。
示例:
#!/usr/bin/perl
# Intitialising the Stack
@stack = (1..3);
# Original stack
print "Original Stack: @stack";
# Scalar to be pushed
$scalar = "scalar";
# Array to be pushed
@array = ("a", "r", "r", "a", "y");
# Hash to be pushed
%hash = ("Geeks" => 10,
"for Geeks" => 20);
# scalars, arrays and hashes can be
# inserted at the same time
push(@stack, ($scalar, @array, %hash));
# Updated Stack after
# Push operations
print("\nUpdated Stack: @stack");
Output:
Original Stack: 1 2 3
Updated Stack: 1 2 3 scalar a r r a y Geeks 10 for Geeks 20
-
Pushing using splice():
语法:拼接(@stack，标量(@stack)，0，list)； T3】参数:
- 函数的作用是:在@stack 的末尾追加“list”。
- “list”可以是标量、数组或哈希。
示例:
```perl
!/usr/bin/perl
Intitialising the Stack
@stack = (1..3);
Original stack
print "Original Stack: @stack";
Scalar to be pushed
$scalar = "scalar";
Array to be pushed
@array = ("a", "r", "r", "a", "y");
Hash to be pushed
%hash = ("Geeks" => 10, "for Geeks" => 20);
scalars, arrays and hashes can be
inserted at the same time
splice(@stack, scalar(@stack), 0, ($scalar, @array, %hash));
Updated Stack after
Push operations
print("\nUpdated Stack: @stack"); ```
Output:
```perl Original Stack: 1 2 3 Updated Stack: 1 2 3 scalar a r r a y Geeks 10 for Geeks 20
```
Popping elements from a Stack
可以使用 pop()函数或拼接()函数进行弹出。
-
Popping using pop():
语法:$ popped _ element = pop(@ stack)； T3】参数:
- 函数的作用是:返回弹出的元素。
- $popped_element 包含从堆栈中弹出的元素。
示例:
```perl
!/usr/bin/perl
Intitialising the Stack
@stack = (1..3);
Original stack
print "Original Stack: @stack";
Topmost element i.e. 3 is
removed and returned
$popped_element = pop(@stack);
Printing popped element
print "\nPopped element: $popped_element";
Updated Stack after
Pop operation
print("\nUpdated Stack: @stack"); ```
Output:
```perl Original Stack: 1 2 3 Popped element: 3 Updated Stack: 1 2
```
-
If the stack is empty, undef is returned. undef is analogous to NULL in Java and None in Python. However, no error is raised.
示例:
```perl
!/usr/bin/perl
Creating a Stack
@stack;
undef is returned since the
stack is empty.
No error is raised.
$popped_element = pop(@stack);
Printing popped element
Since it contains no value,
hence a blank space is returned
print "Popped element: $popped_element"; ```
Output:
```perl Popped element:
```
-
Popping using splice()::
语法:$ popped _ element = splice(@ stack，-1)； T3】参数:
- 函数的作用是:移除堆栈的最后一个元素，然后返回。
- $popped_element 存储返回值。
示例:
```perl
!/usr/bin/perl
Intitialising the Stack
@stack = (1..3);
Original stack
print "Original Stack: @stack";
popping using splice()
$popped_element = splice(@stack, -1);
Printing popped element
print "\nPopped element: $popped_element";
Updated Stack after
Pop operation
print("\nUpdated Stack: @stack"); ```
Output:
```perl Original Stack: 1 2 3 Popped element: 3 Updated Stack: 1 2
```
-
An error is raised, if the stack is empty. The following code raises an error:
```perl use warnings;
!/usr/bin/perl
use warnings;
Creating a Stack
@stack;
popping using splice()
An error is raised here
$popped_element = splice(@stack, -1);
Printing popped element
print "\nPopped element: $popped_element";
Updated Stack after
Pop operation
print("\nStack: @stack"); ```
运行时错误:
在/home/59c 7 c 19979 aa 9e 46564 CD 145 d5fe 5601 . pl 第 6 行的 void 上下文中无用地使用变量。 试图修改不可创建的数组值，下标-1 在/home/59c 7c 19979 aa 9e 46564 CD 145 d5fe 5601 . pl 第 10 行。
