#上文的inject现在用上了module Enumerable def dups inject({}) {|h,v| h[v]=h[v].to_i+1; h}.reject{|k,v| v==1}.keys endend
arr = %w{foo bar baz bar baz qux foo zub}puts arr.dups.inspect# => ["baz", "foo", "bar"]
#替换一inject(Hash.new(0)) {|h,v| h[v] += 1; h}.reject{|k,v| v==1}.keys
这个是比较好理解的
class Array def only_duplicates duplicates = [] self.each {|each| duplicates << each if self.count(each) > 1} duplicates.uniq endend
puts [1,2,2,4,5,1].only_duplicates.inspect==> [1, 2]
require 'benchmark' module Enumerable def map_with_index index = -1 (block_given? && self.class == Range || self.class == Array) ? map { |x| index += 1; yield(x, index) } : self endendclass Array def find_dups inject(Hash.new(0)) { |h,e| h[e] += 1; h }.select { |k,v| v > 1 }.collect { |x| x.first } end def find_dups2 uniq.select{ |e| (self-[e]).size < self.size - 1 } end def find_ndups # also returns the number of items uniq.map { |v| diff = (self.size - (self-[v]).size); (diff > 1) ? [v, diff] : nil}.compact end # cf. http://www.ruby-forum.com/topic/122008 def dups_indices (0...self.size).to_a - self.uniq.map{ |x| index(x) } end def dup_indices(obj) i = -1 ret = map { |x| i += 1; x == obj ? i : nil }.compact #ret = map_with_index { |x,i| x == obj ? i : nil }.compact ret.shift ret end def delete_dups(obj) indices = dup_indices(obj) return self if indices.empty? indices.reverse.each { |i| self.delete_at(i) } self endend array = [1,3,5,5,6,7,9,10,14,18,22,22,4,4,4,3,6]dups = nilBenchmark.bm(14) do |t| t.report('find_dups:') do dups = array.find_dups end end p dups #=> [5, 22, 6, 3, 4]p %w(a b a c c d).dups_indicesp %w(a b a c c d).dup_indices('c')p %w(a b a c c d).delete_dups('a')
class Array def find_dups uniq.map {|v| (self - [v]).size < (self.size - 1) ? v : nil}.compact endend
def mostused(ahash) original_size = ahash.size sizes = {} ahash.uniq.map { |x| sizes[x] = original_size - ((ahash - [x]).size)} sizes.sort_by {|k,v| v}.pop end
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