Ruby笔记四（数组）

#E8.1-1.rb
=begin
数组的索引从0开始，一直到数组的长度减去1；
负数表示从数组末尾开始的索引；
用一对数字来索引数组，第一个数字表示开始位置，第二数字表示从开始位置起的元素数目  
=end
arr=[3,4,5,6,7,8,9]
puts arr[0] #3
puts arr.first #3
puts arr[arr.length-1] #9
puts arr[arr.size-1] #9
puts arr.last #9
puts arr[-1] #9
puts arr[-2] #8
print arr[1..3].join(",") ,"\n" #4, 5, 6
print arr[-3,2] ,"\n" #[7, 8]

#Ruby的数组大小是动态的，你能够随时增加、删除数组元素。
arr=[4,5,6]
print arr.join(", "),"\n" #4, 5, 6

arr[4] = "m" #把4号索引位置元素赋值为"m"
print arr.join(", "),"\n" #4, 5, 6, , m
print arr[3] ,"\n" #打印3号索引位置元素 #nil

arr.delete_at(3) #删除3号索引位置元素
print arr.join(", "),"\n" #4, 5, 6, m

arr[2] = ["a","b","c"] #把2号索引位置元素赋值为["a","b","c"]
print arr.join(", "),"\n" #4, 5, a, b, c, m
print arr[2].join(",") ,"\n" #打印2号索引位置元素 #a,b,c

arr[0..1] = [7,"h","b"] #把0..1号元素替换为7,"h","b"
print arr.join(", "),"\n" #7, h, b, a, b, c, m

arr.push("b" ) #加入元素"b"
print arr.join(", "),"\n" #7, h, b, a, b, c, m, b

arr.delete(["a","b","c"] ) #删除元素["a","b","c"]
print arr.join(", "),"\n" #7, h, b, m, b

arr.delete("b") #删除所有元素"b"
print arr.join(", "),"\n" #7, h, m

arr.insert(3,"d") #在3号索引位置插入元素"d"
print arr.join(", "),"\n" #7, h, m, d

arr<<"f"<<2 #加入元素"f"；加入元素2
print arr.join(", "),"\n" #7, h, m, d, f, 2

arr.pop #删除尾元素
print arr.join(", "),"\n" #7, h, m, d, f

arr.shift #删除首元素
print arr.join(", "),"\n" #h, m, d, f

arr.clear #清空数组arr
print arr.join(", "),"\n" 

#获取新数组

a=%W(a b c d e f g h i j k)

p a #=>["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k"]

a2=a.values_at(1,3,5) #获取指定索引数组元组，构建一个新的数组

p a2 #=>["b", "d", "f"]

 

#数组运算
aaaa=["aa",4,5,"bb"]
bbbb=[4,1,3,2,5]
print (aaaa + bbbb).join(" ") ,"\n" #aa 4 5 bb 4 1 3 2 5
print (aaaa * 2).join(" ") ,"\n" #aa 4 5 bb aa 4 5 bb
print (bbbb - aaaa).join(" ") ,"\n" #1 3 2

#并运算；交运算
print (aaaa | bbbb).join(",") ,"\n" #aa,4,5,bb,1,3,2
print (aaaa & bbbb).join(",") ,"\n" #4,5

a11=[1,2,3]
a12=[3,4,5]
#获取数组的并集
a13=a11|a12 
p a13 #=>[1, 2, 3, 4, 5]
#获取数组的交集
a14=a11&a12
p a14  #=>[3]
#获取差集
a15=a11-a12
p a15  #=>[1, 2]
#删除重复的元组
a=[1,2,3,4,3,2,1]
b= a.uniq 
p a   #=>1, 2, 3, 4, 3, 2, 1]
p b   #=>1, 2, 3, 4]
b=a.uniq! #uniq!会直接从数组中删除重复的元素
p a   #=>1, 2, 3, 4]
p b   #=>1, 2, 3, 4]

#排序；倒置
print bbbb.sort().join(",") ,"\n" #1,2,3,4,5
print aaaa.reverse.join(",") ,"\n" #bb,5,4,aa

 

#collect方法 以数组的形式返回操作结果

a=%w(foo nbar nbuz)

b=a.collect{|i| i.upcase}

p b #=>["FOO", "NBAR", "NBUZ"]

 

#数组初始化，如果数组元素是对象或者hash对象，应当使用指定的block作为数组初始化元素
a=Array.new(3,[0,0])
p a #=>[[0, 0], [0, 0], [0, 0]]
a[0][1]=1
p a #=>[[0, 1], [0, 1], [0, 1]],this result is‘t what we expect.
a=Array.new(3){[0,0]}
p a #=>[[0, 0], [0, 0], [0, 0]]
a[0][1]=1
p a  #=>[[0, 1], [0, 0], [0, 0]]