Ruby string and array maximization problems, ruby Problems

Ruby string and array maximization problems, ruby Problems

Max Method

b=[1,3,55,777,2,4,6,8,0]

For numeric data, max obtains the maximum value of the array, and min obtains the minimum value of the array.

b.max => 777
b.min => 0

It has no practical significance for comparing the size of string arrays,
The example in ruby is

# enum.max         -> obj
# enum.max { |a, b| block } -> obj
#a = %w(albatross dog horse)
#a.max          => "horse"
# a.max { |a, b| a.length <=> b.length } #=> "albatross"

Lab in practice

d=%w(albatross dog horse ddd dasgfds)
d.max => "horse"

A little strange. What's going on?
Therefore, a relatively intuitive numeric string is printed.

a = ["1", "3", "55", "777", "2", "4", "6", "8", "0"]
def max(first,*rest) 
 max=first 
 rest.each do |x|
  p "---#{x}---#{max}"
  max=x if x>max 
  p "---#{x}---#{max}"
  max 
end

Run
Copy codeThe Code is as follows: a. max
Result:

"---3---1"
"---3---3"
"---55---3"
"---55---55"
"---777---55"
"---777---777"
"---2---777"
"---2---777"
"---4---777"
"---4---777"
"---6---777"
"---6---777"
"---8---777"
"---8---8"
"---0---8"
"---0---8"
 => "8"

The problem arises. "8"> "777" => true, test again.

"7" > "777" => false
"6" > "777" => false
"9" > "777" => true
"10" > "777" => false
"11" > "777" => false
"70" > "777" => false
"80" > "777" => true

This crashes, and the rule is not friendly, because the max method is used to compare the size, which is previously considered to be determined by ASCII encoding, this problem was found today when I looked at the sort Sorting Problem. In fact, this is the maximum value obtained by the dictionary sorting method.

Next let's take a look at the sort in Ruby:

Sort sorting method

ary.sort          -> new_ary
ary.sort { |a, b| block } -> new_ary
enum.sort_by { |obj| block }  -> array
enum.sort_by          -> an_enumerator

Instance

h=['1','3','13','10','7']
 A. p h.sort
 B. p h.sort{|a,b| a.to_i <=> b.to_i}
 C. p h.sort_by{|x| x.to_i}


 

	
  


 

The output is as follows:

A. ["1", "10", "13", "3", "7"] 
B. ["1", "3", "7", "10", "13"] 
C. ["1", "3", "7", "10", "13"]


 

	
  


 

1. When no block is specified, the default sort of sort is ordered by the dictionary.
2. If a block is specified, sorting the values is the size of the value of the block-making method.
3. The sort_by method sorts the results generated by the code that executes the block. Each element is called only once, which is faster than B.

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