《Rubu基础教程第五版》第十三章笔记 数组类

数组类 Array

数组的创建方法

Array.new 可以接收0，1，2是那种参数

>> Array.new
=> []
>> Array.new(5)
=> [nil, nil, nil, nil, nil]
>> Array.new(5,3)
=> [3, 3, 3, 3, 3]
>> 

 

使用%w或%i来创建

>> %w(hello world)
=> ["hello", "world"]
>> %i(hello world)
=> [:hello, :world]
>> 

 

使用to_a创建

>> (2..10).to_a
=> [2, 3, 4, 5, 6, 7, 8, 9, 10]
>> hash = {"abc"=>1, "cde"=>2}
=> {"abc"=>1, "cde"=>2}
>> hash.to_a
=> [["abc", 1], ["cde", 2]]
>> 

 

使用字符串的spilt方法

=> "hello world"
>> str.split()
=> ["hello", "world"]
>> 

 

索引的使用方法

a[n] 取n索引的元素

a[n..m]或a[n...m]取n到m的元素，或者n到m-1的元素

a[n,len]从n索引开始的，len个元素

 

a.at(n) 等价 a[n]

a.slice(n) 等价 a[n]

a.slice(n..m)等价a[n..m]

a.slice(n, m) 等价a[n, m]

 

替换元素

同样支持切片赋值

irb(main):002:0> arr = (1..5).to_a
=> [1, 2, 3, 4, 5]
irb(main):003:0> arr[1..2]
=> [2, 3]
irb(main):004:0> arr[1..2] = [7,8,9,]
=> [7, 8, 9]
irb(main):005:0> arr
=> [1, 7, 8, 9, 4, 5]
irb(main):006:0> 

 

插入元素

插入元素比较有意思，书中用的[x,y]形式

irb(main):006:0> arr = ('a'.."f").to_a
=> ["a", "b", "c", "d", "e", "f"]
irb(main):007:0> arr[2,0] = ["x", "y"]
=> ["x", "y"]
irb(main):008:0> arr
=> ["a", "b", "x", "y", "c", "d", "e", "f"]
irb(main):009:0> arr[5..5] = ["5", "6"]
=> ["5", "6"]
irb(main):010:0> arr
=> ["a", "b", "x", "y", "c", "5", "6", "e", "f"]
irb(main):011:0> 
irb(main):011:0> arr[7...7] = ["7", "7"]
=> ["7", "7"]
irb(main):012:0> arr
=> ["a", "b", "x", "y", "c", "5", "6", "7", "7", "e", "f"]

 

通过arr[n,0]或者arr[n...n]对n的位置进行插入元素，元素用arr的形式

起始就像切片赋值的方式进行了插入

 

取出指定的值获取的元素组成新的arr

irb(main):013:0> arr
=> ["a", "b", "x", "y", "c", "5", "6", "7", "7", "e", "f"]
irb(main):014:0> arr.values_at(1,2,3,7,99)
=> ["b", "x", "y", "7", nil]
irb(main):015:0> 

 

ruby没有集合的概念，数组就可以直接拿来当集合用

交集 & 并集 |

是只有一个符号

差集 -

还可以合并用 +

 

模拟栈或者队列形式操作数组

对数组的开头进行操作 追加元素 unshift 删除元素 shift 引用元素 first

            结尾进行操作  追加元素push   删除元素 pop   引用元素 last

 

=> ["b", "x", "y", "c", "5", "6", "7", "7", "e", "f"]
irb(main):019:0> arr.size
=> 10
irb(main):020:0> arr.first
=> "b"
irb(main):021:0> arr.first
=> "b"
irb(main):022:0> arr.size
=> 10
irb(main):023:0> arr.methods
=> [:to_h, :include?, :at, :fetch, :last, :union, :difference, :push, :append, :pop, :shift, :unshift, :each_index, :join, :rotate, :rotate!, :sort!, :sort_by!, :collect!, :map!, :select!, :filter!, :keep_if, :values_at, :delete_at, :delete_if, :reject!, :transpose, :fill, :assoc, :rassoc, :uniq!, :compact, :compact!, :flatten, :flatten!, :shuffle!, :shuffle, :*, :+, :permutation, :&, :repeated_permutation, :combination, :sample, :repeated_combination, :product, :bsearch, :-, :sort, :bsearch_index, :count, :find_index, :select, :filter, :reject, :collect, :map, :first, :all?, :any?, :one?, :none?, :reverse_each, :zip, :take, :take_while, :drop, :drop_while, :cycle, :sum, :uniq, :|, :insert, :<=>, :<<, :index, :rindex, :replace, :==, :clear, :pack, :[], :[]=, :empty?, :eql?, :max, :min, :reverse, :inspect, :concat, :prepend, :reverse!, :length, :size, :each, :to_ary, :delete, :to_a, :to_s, :slice, :slice!, :dig, :hash, :to_set, :find, :entries, :sort_by, :grep, :grep_v, :detect, :find_all, :flat_map, :collect_concat, :inject, :reduce, :partition, :group_by, :minmax, :min_by, :max_by, :minmax_by, :member?, :each_with_index, :each_entry, :each_slice, :each_cons, :each_with_object, :chunk, :slice_before, :slice_after, :slice_when, :chunk_while, :chain, :lazy, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :tap, :instance_variable_get, :instance_variable_set, :instance_variables, :singleton_method, :method, :public_send, :define_singleton_method, :public_method, :extend, :to_enum, :enum_for, :===, :=~, :!~, :respond_to?, :freeze, :object_id, :send, :display, :nil?, :class, :singleton_class, :clone, :dup, :itself, :yield_self, :then, :taint, :tainted?, :untaint, :untrust, :untrusted?, :trust, :frozen?, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :equal?, :!, :__id__, :instance_exec, :!=, :instance_eval, :__send__]
irb(main):024:0> arr
=> ["b", "x", "y", "c", "5", "6", "7", "7", "e", "f"]
irb(main):025:0> arr.push("push")
=> ["b", "x", "y", "c", "5", "6", "7", "7", "e", "f", "push"]
irb(main):026:0> arr.unshift("unshift")
=> ["unshift", "b", "x", "y", "c", "5", "6", "7", "7", "e", "f", "push"]
irb(main):027:0> arr.pop
=> "push"
irb(main):028:0> arr.last
=> "f"
irb(main):029:0> 

 

跟Python比就一个pop是通用的

 

数组的主要方法

unshift 插入头部数据

<< 跟 push 一样

a.concat(b) 等于 +号 相同与Python的extend

切片赋值前面已经都讲过了

 

由于Ruby跟Python一样属于引用传参，所以当两个变量名指向同一个arr，任何一个操作，都会影响另外一个

可以通过freeze冻结，通过dup赋值一个解冻的

irb(main):034:0> arr.freeze
=> ["a", "b", "c"]
irb(main):035:0> arr[0]= 9
Traceback (most recent call last):
        4: from /usr/bin/irb:23:in `<main>'
        3: from /usr/bin/irb:23:in `load'
        2: from /Library/Ruby/Gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
        1: from (irb):35
FrozenError (can't modify frozen Array)
irb(main):036:0> b = arr.dup
=> ["a", "b", "c"]
irb(main):037:0> b.pop
=> "c"
irb(main):038:0> b
=> ["a", "b"]
irb(main):040:0> arr
=> ["a", "b", "c"]
irb(main):041:0> 

 Python中集合也可以用freeze，这样可以当做一种深拷贝使用不错

 

从数组中删除元素

irb(main):046:0> b
=> ["a", nil, "b", nil]
irb(main):047:0> b.compact
=> ["a", "b"]
irb(main):048:0> b
=> ["a", nil, "b", nil]
irb(main):049:0> b.compact!
=> ["a", "b"]
irb(main):050:0> b
=> ["a", "b"]
irb(main):051:0> 

 compact删除重复元素，如果带!会对自身进行修改

 

delete方法，删除执行名称的元素，只要名字相同可以删除多个

irb(main):052:0> b << "b"
=> ["a", "b", "b"]
irb(main):053:0> b.delete "b"
=> "b"
irb(main):054:0> b
=> ["a"]
irb(main):055:0> 

 

delete_at方法，删除指定位置的元素

irb(main):058:0> b
=> ["a", 1, 2, 3, 4, 5]
irb(main):059:0> b.delete_at(-1)
=> 5
irb(main):060:0> b
=> ["a", 1, 2, 3, 4]
irb(main):061:0> 

 

delete_if 删除后面指定条件

reject 排除该条件以外的

reject! 改变自身

irb(main):066:0> b
=> [1, 2, 3, 4]
irb(main):067:0> b.reject{|n| n>1}
=> [1]
irb(main):068:0> b.delete_if{|n| n<3}
=> [3, 4]
irb(main):069:0> b
=> [3, 4]
irb(main):070:0> 

 

删除指定元素

slice!

irb(main):072:0> arr = %w(a b c d e f g)
=> ["a", "b", "c", "d", "e", "f", "g"]
irb(main):073:0> arr.slice!(0)
=> "a"
irb(main):074:0> arr
=> ["b", "c", "d", "e", "f", "g"]
irb(main):075:0> arr.slice!(1..2)
=> ["c", "d"]
irb(main):076:0> arr
=> ["b", "e", "f", "g"]
irb(main):077:0> arr.slice!(1,9)
=> ["e", "f", "g"]
irb(main):078:0> arr
=> ["b"]
irb(main):079:0> 

 

uniq 去重的

uniq! 自身去重

不掩饰了

 

shift 取首个元素

pop 取最后一个元素

 

替换数组元素

collect 与map collect返回的还是一个arr，现在测试用起来

irb(main):085:0> arr
=> [1, 2, 3, 4, 5]
irb(main):087:0> arr.collect!{|n|  n**n}
=> [1, 4, 27, 256, 3125]
irb(main):088:0> arr
=> [1, 4, 27, 256, 3125]
irb(main):089:0> arr.map{|n| n+1}
=> [2, 5, 28, 257, 3126]
irb(main):090:0> arr.map!{|n| n+1}
=> [2, 5, 28, 257, 3126]
irb(main):091:0> arr
=> [2, 5, 28, 257, 3126]
irb(main):092:0> arr.map!{|n| Math.sqrt(n)}
=> [1.4142135623730951, 2.23606797749979, 5.291502622129181, 16.0312195418814, 55.910642993977454]
irb(main):093:0> arr
=> [1.4142135623730951, 2.23606797749979, 5.291502622129181, 16.0312195418814, 55.910642993977454]
irb(main):094:0> 

 经过测试，没发现map跟collect的差别

 

fill 填充

一个参数，全部填充这个

fill(value)

fill(value, begin)

fill(value, begin, end)

fill(value, n..m)

irb(main):096:0> arr.fill(999)
=> [999, 999, 999, 999, 999]
irb(main):097:0> arr
=> [999, 999, 999, 999, 999]
irb(main):098:0> arr.fill(0,2)
=> [999, 999, 0, 0, 0]
irb(main):099:0> arr.fill(6,1,2)
=> [999, 6, 6, 0, 0]
irb(main):100:0> arr.fill(6,3..5)
=> [999, 6, 6, 6, 6, 6]
irb(main):101:0> 

 

flatten

flatten!修改自身，取出嵌套的效果，变成一个没有嵌套的数组

irb(main):101:0> a = [1,[2,[3]],4,[[5]]]
=> [1, [2, [3]], 4, [[5]]]
irb(main):102:0> a.flatten!
=> [1, 2, 3, 4, 5]
irb(main):103:0> a
=> [1, 2, 3, 4, 5]
irb(main):104:0> 

 

reverse反转

reverse!自身反转

 

sort排序，默认都是从小到大

sort_by 必须通过{}填写参数

前面章节，已经介绍过具体用法

 

数组与迭代器

collect返回个一个array对象

irb(main):104:0> a = 1..5
=> 1..5
irb(main):105:0> b = a.collect{|n| n**n}
=> [1, 4, 27, 256, 3125]
irb(main):106:0> b
=> [1, 4, 27, 256, 3125]
irb(main):107:0> a
=> 1..5
irb(main):108:0> a.map{|n| n**n}
=> [1, 4, 27, 256, 3125]
irb(main):109:0> 

 

处理数组中的元素

for 循环处理

list = [1, 3, 7, 9]
sum = 0
for i in 0...list.size
  sum += list[i]
 end

print "合计为#{sum}"

 

另外用each或each_with_index 或者对arr进行pop方法，调用 while

while item = a.pop

  ## 对item进行处理

end

 

创建矩阵

a = Array.new(3, [0,0,0])

这个创建的举证，每个元素指向同一个地址

 

需要不同的地址，要这么写

shijianongdeMBP:chapter_13 shijianzhong$ cat t.rb 
a = Array.new(3) do
  [0, 0, 0]
end

p a

 

还有一种.new后面通过{}的形式创建array

irb(main):001:0> Array.new(5){|i| i + 1}
=> [1, 2, 3, 4, 5]
irb(main):002:0> Array.new(5){|i| i ** i}
=> [1, 1, 4, 27, 256]
irb(main):003:0> Array.new(5){|i| i}
=> [0, 1, 2, 3, 4]
irb(main):004:0> 

 

同时访问多个数组

就写一个zip的用法

shijianongdeMBP:chapter_13 shijianzhong$ cat sum_with_zip.rb 
ary1 = [1, 2, 3, 5]
ary2 = [10, 20, 30, 40, 50]
ary3 = 100.step(500, 100)

result = []
ary1.zip(ary2, ary3) do |a, b, c|
  result.push( a + b + c)
end

p result

 

irb(main):001:0> [].methods
=> [:to_h, :include?, :at, :fetch, :last, :union, :difference, :push, :append, :pop, :shift, :unshift, :each_index, :join, :rotate, :rotate!, :sort!, :sort_by!, :collect!, :map!, :select!, :filter!, :keep_if, :values_at, :delete_at, :delete_if, :reject!, :transpose, :fill, :assoc, :rassoc, :uniq!, :compact, :compact!, :flatten, :flatten!, :shuffle!, :shuffle, :*, :+, :permutation, :&, :repeated_permutation, :combination, :sample, :repeated_combination, :product, :bsearch, :-, :sort, :bsearch_index, :count, :find_index, :select, :filter, :reject, :collect, :map, :first, :all?, :any?, :one?, :none?, :reverse_each, :zip, :take, :take_while, :drop, :drop_while, :cycle, :sum, :uniq, :|, :insert, :<=>, :<<, :index, :rindex, :replace, :==, :clear, :pack, :[], :[]=, :empty?, :eql?, :max, :min, :reverse, :inspect, :concat, :prepend, :reverse!, :length, :size, :each, :to_ary, :delete, :to_a, :to_s, :slice, :slice!, :dig, :hash, :to_set, :find, :entries, :sort_by, :grep, :grep_v, :detect, :find_all, :flat_map, :collect_concat, :inject, :reduce, :partition, :group_by, :minmax, :min_by, :max_by, :minmax_by, :member?, :each_with_index, :each_entry, :each_slice, :each_cons, :each_with_object, :chunk, :slice_before, :slice_after, :slice_when, :chunk_while, :chain, :lazy, :instance_variable_defined?, :remove_instance_variable, :instance_of?, :kind_of?, :is_a?, :tap, :instance_variable_get, :instance_variable_set, :instance_variables, :singleton_method, :method, :public_send, :define_singleton_method, :public_method, :extend, :to_enum, :enum_for, :===, :=~, :!~, :respond_to?, :freeze, :object_id, :send, :display, :nil?, :class, :singleton_class, :clone, :dup, :itself, :yield_self, :then, :taint, :tainted?, :untaint, :untrust, :untrusted?, :trust, :frozen?, :methods, :singleton_methods, :protected_methods, :private_methods, :public_methods, :equal?, :!, :__id__, :instance_exec, :!=, :instance_eval, :__send__]
irb(main):002:0> 

 内置的方法实在太多了

 

标签：arr,第五版,..,元素,999,Rubu,基础教程,irb,main
来源： https://www.cnblogs.com/sidianok/p/13045049.html