diff --git a/01-hello.rb b/01-hello.rb
index e0e7bbf..0380a8f 100644
--- a/01-hello.rb
+++ b/01-hello.rb
@@ -1,8 +1,5 @@
 # 题目: 输入名字，输出 "Hello, 名字"
 
-print "请输入你的名字，然后按 Enter: "
+print "请输入你的\"名字\"，然后按 Enter: "
 your_name = gets
-
-# ...
-
-puts "(请替换成最后的答案)"
\ No newline at end of file
+puts "hi,#{your_name}"
diff --git a/02-variable.rb b/02-variable.rb
index a5a4753..88f9260 100644
--- a/02-variable.rb
+++ b/02-variable.rb
@@ -7,7 +7,10 @@
 puts "b 是 #{b}"
 
 # ...
+c = a
+a = b
+b = c
+
 
 puts "a 应该是 2，现在是 #{a}"
 puts "b 应该是 1，现在是 #{b}"
-
diff --git a/03-triangle.rb b/03-triangle.rb
index fafec03..d38648a 100644
--- a/03-triangle.rb
+++ b/03-triangle.rb
@@ -1,11 +1,11 @@
 # 题目: 使用者输入直角三角形的宽和高，输出三角形的面积
 
 print "请输入直角三角形的高，然后按 Enter: "
-a = gets
+a = (gets).to_i
 
 print "请输入直角三角形的底边，然后按 Enter: "
-b = gets
-
+b = (gets).to_i
+c = (a*b)/2
 # .....
 
-puts "直角三角形的面积是: _________"
\ No newline at end of file
+puts "直角三角形的面积是: ___#{c}______"
diff --git a/04-pizzas.rb b/04-pizzas.rb
index 4c2521f..3918da7 100644
--- a/04-pizzas.rb
+++ b/04-pizzas.rb
@@ -5,8 +5,8 @@
 
 print "请输入有多少人要吃，然后按 Enter: "
 people = gets
+#left = pizzas.to_i - (pizzas.to_i / people.to_i)*people.to_i
+left = pizzas.to_i % people.to_i
 
-# .....
-
-puts "每人可分得几片: _________ 片"
-puts "还剩下几片: _________ 片"
\ No newline at end of file
+puts "每人可分得几片: #{ pizzas.to_i / people.to_i}片"
+puts "还剩下几片: #{left}片"
diff --git a/05-bmi.rb b/05-bmi.rb
index 67efdff..eb262d0 100644
--- a/05-bmi.rb
+++ b/05-bmi.rb
@@ -10,8 +10,17 @@
 print "请输入您的身高(厘米)，然后按 Enter: "
 height = gets
 
-# .....
+bmi = weight.to_f/(height.to_f*height.to_f)
 
-puts "您的 BMI 是: _________"
+if bmi>=24.0
+  result = "过重"
+elsif bmi<18.5
+  result = "过轻"
+else
+  result = "正常"
+end
 
-puts "您的 BMI 结果是: _________(过轻或正常或过重)"
\ No newline at end of file
+
+puts "您的 BMI 是: #{bmi}"
+
+puts "您的 BMI 结果是: #{result}"
diff --git a/06-interger-positive.rb b/06-interger-positive.rb
index a240f5f..5bdb2d6 100644
--- a/06-interger-positive.rb
+++ b/06-interger-positive.rb
@@ -2,9 +2,22 @@
 
 
 print "请输入一个整数，然后按 Enter: "
-x = gets
+y = (gets).to_i
+puts y
+if y == 0
+  x = "0"
+elsif y > 0
+  x = "正数"
+else
+  x = "负数"
+end
 
+if y % 2 == 0
+  z = "偶数"
+else
+  z = "奇数"
+end
 # ....
 
-puts "这个数是_____ (正数或零或负数)"
-puts "这个数是_____ (偶数或奇数)"
\ No newline at end of file
+puts "这个数是#{x}"
+puts "这个数是#{z} (偶数或奇数)"
diff --git a/07-abcde.rb b/07-abcde.rb
index 5d0c8c3..bde93f5 100644
--- a/07-abcde.rb
+++ b/07-abcde.rb
@@ -9,14 +9,28 @@
 #     当 z < 0 输出 "E"
 
 print "请输入一个整数x，然后按 Enter: "
-x = gets
+x = (gets).to_i
 
 print "请输入一个整数y，然后按 Enter: "
-y = gets
+y = (gets).to_i
 
 print "请输入一个整数z，然后按 Enter: "
-z = gets
+z = (gets).to_i
 
-# ....
+if x < 0
+  result = "A"
+elsif x > 0
+  if y > 0 && z > 0
+    result = "B"
+  elsif y >0 && z < 0
+    result = "C"
+  elsif y < 0 && z > 0
+    result = "D"
+  else
+    result = "E"
+  end
+else
+  result = "0"
+end
 
-puts "结果是________(A或B或C或D或E)"
\ No newline at end of file
+puts "结果是#{result}"
diff --git a/08-find-max.rb b/08-find-max.rb
index 9e6e643..a359a1f 100644
--- a/08-find-max.rb
+++ b/08-find-max.rb
@@ -1,14 +1,40 @@
 # 题目: 使用者输入 x,y,z，请输出三个数中最大的数
 
 print "请输入一个数字x，然后按 Enter: "
-x = gets
+x = (gets).to_i
 
 print "请输入一个数字y，然后按 Enter: "
-y = gets
+y = (gets).to_i
 
 print "请输入一个数字z，然后按 Enter: "
-z = gets
+z = (gets).to_i
 
-# ....
+if x > y
+  if x > z
+    result = "x"
+  elsif x < z
+    result = "z"
+  else
+    result = "x和z 并列最大"
+  end
+elsif x = y
+  if x > z
+    result = "x和y 并列最大"
+  elsif x < z
+    result = "z"
+  else
+    result = "x y z 一样大"
+  end
+else
+  if x >= z
+    result = "Y"
+  elsif y > z
+    result = "Y"
+  elsif y < z
+    result = "z"
+  else
+    result = "y和z 并列最大"
+  end
+end
 
-puts "最大的数是 ________(x或y或z)"
\ No newline at end of file
+puts "最大的数是 #{result}  (x或y或z)"
diff --git a/09-function.rb b/09-function.rb
index b1f922d..2d9b462 100644
--- a/09-function.rb
+++ b/09-function.rb
@@ -1,15 +1,15 @@
 # 题目: 输入直角三角形的宽和高，输出三角形的面积
 
 def calculate_area(a, b)
-  # ....
+  return (a*b)/2
 end
 
 print "请输入直角三角形的高，然后按 Enter: "
-a = gets
+a = (gets).to_i
 
 print "请输入直角三角形的底边，然后按 Enter: "
-b = gets
+b = (gets).to_i
 
 answer = calculate_area(a,b)
 
-puts "直角三角形的面积是: #{answer}"
\ No newline at end of file
+puts "直角三角形的面积是: #{answer}"
diff --git a/10-function.rb b/10-function.rb
index bb450fb..584c44c 100644
--- a/10-function.rb
+++ b/10-function.rb
@@ -1,19 +1,46 @@
 # 题目: 使用者输入 x,y,z，请输出三个数中最大的数
 
 def find_max(x, y, z)
+  if x > y
+    if x > z
+      return result = "x"
+    elsif x < z
+      return result = "z"
+    else
+      return result = "x和z 并列最大"
+    end
+  elsif x = y
+    if x > z
+      return result = "x和y 并列最大"
+    elsif x < z
+      return result = "z"
+    else
+      return result = "x y z 一样大"
+    end
+  else
+    if x >= z
+      return result = "Y"
+    elsif y > z
+      return result = "Y"
+    elsif y < z
+      return result = "z"
+    else
+      result = "y和z 并列最大"
+    end
+  end
 end
 
 print "请输入一个数字x，然后按 Enter: "
-x = gets
+x = (gets).to_f
 
 print "请输入一个数字y，然后按 Enter: "
-y = gets
+y = (gets).to_f
 
 print "请输入一个数字z，然后按 Enter: "
-z = gets
+z = (gets).to_f
 
 # ....
 
 answer = find_max(x,y,z)
 
-puts "最大的数是 #{answer}"
\ No newline at end of file
+puts "最大的数是 #{answer}"
diff --git a/11-seven.rb b/11-seven.rb
index 26c221d..b308999 100644
--- a/11-seven.rb
+++ b/11-seven.rb
@@ -3,7 +3,8 @@
 i = 1
 while ( i <= 100 )
 
-  # ....
-
+  if i%7 == 0
+    puts i
+  end
   i+=1
-end
\ No newline at end of file
+end
diff --git a/12-sum-even.rb b/12-sum-even.rb
index 73879bb..5a74ad9 100644
--- a/12-sum-even.rb
+++ b/12-sum-even.rb
@@ -5,9 +5,11 @@
 
 while ( i <= 100 )
 
-  # ....
+  if i % 2 == 0
+    total += i
+  end
 
   i+=1
 end
 
-puts total
\ No newline at end of file
+puts total
diff --git a/13-nn.rb b/13-nn.rb
index ac0a43b..71b76cb 100644
--- a/13-nn.rb
+++ b/13-nn.rb
@@ -1,11 +1,12 @@
 # 题目: 输入一个数字 N，输出 N * N 乘法表
 
 print "请输入数字 N，然后按 Enter: "
-n = gets
-
-# while ( ... )
-#   while ( ...)
-#
-#   end
-# end
-
+n = (gets).to_i
+i = 1
+while ( i < (n+1) )
+  # while ( ...)
+  #
+  # end
+  puts "#{n} * #{i} = #{i*n}"
+  i += 1
+end
diff --git a/14-prime.rb b/14-prime.rb
index 8cf1692..c3b851d 100644
--- a/14-prime.rb
+++ b/14-prime.rb
@@ -1,7 +1,17 @@
 # 输入一个数字 N，请检查是不是质数
 
 def is_prime(n)
-# ....
+  i = 2
+  r = true
+  while i < n
+
+    if n % i == 0
+      r = false
+      break
+    end
+    i +=1
+  end
+  return r
 end
 
 print "请输入数字 N，然后按 Enter: "
diff --git a/15-guess-number.rb b/15-guess-number.rb
index 48f9dca..aa2c5f8 100644
--- a/15-guess-number.rb
+++ b/15-guess-number.rb
@@ -5,13 +5,18 @@
 while (true)
   print "请猜一个 0~99 的数字 N，然后按 Enter: "
   n = gets
-
-  #puts "太低了，再猜一次"
-  #puts "太高了，再猜一次"
-
-  if n.to_i == target
+  if n.to_i < target
+    puts "低了，再猜一次"
+  elsif n.to_i > target
+    puts "太高了，再猜一次"
+  else
     puts "恭喜猜中啦! "
     break
   end
 
-end
\ No newline at end of file
+  # if n.to_i == target
+  #   puts "恭喜猜中啦! "
+  #   break
+  # end
+
+end
diff --git a/16-array-sum.rb b/16-array-sum.rb
index 9b4910b..49d74ff 100644
--- a/16-array-sum.rb
+++ b/16-array-sum.rb
@@ -1,11 +1,16 @@
 # 给定一阵列内含数字，输出最大值
 
 def find_max(array)
-  #....
+  m = array[0]
+  array.each do |i|
+    if m <= i
+      m = i
+    end
+  end
+  return m
 end
-
-arr = [8, 12, 36, 53, 9, 75, 3, 71, 59, 88]
+# 直接用max也行。
+arr = [8, 12, 36, 93, 9, 75]
 
 max = find_max(arr)
 puts "Max is #{max}" # 应该是 88
-
diff --git a/17-array-stats.rb b/17-array-stats.rb
index 0af81bb..7601f66 100644
--- a/17-array-stats.rb
+++ b/17-array-stats.rb
@@ -12,9 +12,26 @@
   end
 end
 
+total = 0
+max = arr[0]
+min = arr[0]
+
+arr.each do |i|
+  total = total + i
+  if max <= i
+    max = i
+  end
+
+  if min >=i
+    min = i
+  end
+end
+
+avg = total.to_f / arr.size
+
 puts arr.to_s
 
-puts "总和是 _____"
-puts "平均是 _____"
-puts "最大值是 _____"
-puts "最小值是 _____"
\ No newline at end of file
+puts "总和是#{total}"
+puts "平均是#{avg}"
+puts "最大值是#{max}"
+puts "最小值是#{min}"
diff --git a/18-square.rb b/18-square.rb
index 226e1c1..d55e9e8 100644
--- a/18-square.rb
+++ b/18-square.rb
@@ -3,8 +3,12 @@
 arr = []
 
 print "请输入数字 N，然后按 Enter: "
-n = gets
-
+n = (gets).to_i
+i = 0
+while i < n
+  arr << i*i
+  i +=1
+end
 # ...
 
-puts arr.to_s
\ No newline at end of file
+puts arr.to_s
diff --git a/19-filter.rb b/19-filter.rb
index ef7e515..19b76ca 100644
--- a/19-filter.rb
+++ b/19-filter.rb
@@ -1,9 +1,15 @@
 # 给定一阵列内含数字，输出另一个数组只包含偶数
 
 def filter_even(arr)
-  #...
+  even_arr = []
+  arr.each do |i|
+    if i % 2 == 0
+      even_arr.push(i)
+    end
+  end
+  even_arr
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
-puts filter_even(arr).to_s # 应该是 [68, 42, 46, 46, 86]
\ No newline at end of file
+puts filter_even(arr).to_s # 应该是 [68, 42, 46, 46, 86]
diff --git a/20-sorting.rb b/20-sorting.rb
index 5f82c08..d5bc776 100644
--- a/20-sorting.rb
+++ b/20-sorting.rb
@@ -2,10 +2,16 @@
 # Hint: 可用 arr.sort 排序，和 arr.uniq 去除重复
 
 def filter_even(arr)
-  #...
+  even_arr = []
+  arr.each do |i|
+    if i % 2 == 0
+      even_arr.push(i)
+    end
+  end
+  even_arr.uniq.sort
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
 
-puts "________" # 应该是 [42, 46, 68, 86]
\ No newline at end of file
+puts filter_even(arr).to_s # 应该是 [42, 46, 68, 86]
diff --git a/21-selection-sort.rb b/21-selection-sort.rb
index e5e7eae..de0312b 100644
--- a/21-selection-sort.rb
+++ b/21-selection-sort.rb
@@ -2,11 +2,32 @@
 # https://zh.wikipedia.org/wiki/选择排序
 
 def selection_sort(arr)
-  #...
+  temp = []
+  i = 0
+  l = arr.size - 1
+  # 双循环：外面的循环，是按顺序从前向后依次提取值，直到倒数第二个结束。
+  # 嵌套的循环，是让外循环提取的值和后续的值进行对比。
+  # 所以两个循环的次数都是n-1
+  while i < l
+    min = i
+    j = i + 1
+    while j < arr.size
+      if arr[min] > arr[j]
+        min = j
+      end
+      j += 1
+    end
+    temp = arr[i]
+    arr[i] = arr[min]
+    arr[min] = temp
+
+    i += 1
+  end
+  return arr
 end
 
 arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
 
 answer = selection_sort(arr)
 
-puts answer.to_s # 应该是 [1, 7, 9, 42, 46, 46, 68, 77, 86, 91]
\ No newline at end of file
+puts answer.to_s # 应该是 [1, 7, 9, 42, 46, 46, 68, 77, 86, 91]
diff --git a/22-missing.rb b/22-missing.rb
index 6898714..27dc05e 100644
--- a/22-missing.rb
+++ b/22-missing.rb
@@ -1,7 +1,24 @@
 # 给定一阵列内含数字，请输出 0~9 中不见的数字
 
 def find_missing(arr)
-  # ...
+  contrast = [1,2,3,4,5,6,7,8,9]
+  result = []
+
+  contrast.each do |c|
+    arr_have = false
+
+    arr.each do |a|
+      if c == a
+        arr_have = true
+        break
+      end
+    end
+    if arr_have == false
+      result << c
+    end
+  end
+
+  return result
 end
 
 answer = find_missing( [2,2,1,5,8,4] )
diff --git a/23-hash-max.rb b/23-hash-max.rb
index 6fb227e..c52d21b 100644
--- a/23-hash-max.rb
+++ b/23-hash-max.rb
@@ -1,7 +1,15 @@
 # 给定一 Hash，输出有最大 value 的 key
 
 def find_max(hash)
-  # ...
+  arr = hash.values
+  arr_max = arr.max
+  re_string = ''
+  hash.each do |key, value|
+    if value == arr_max
+        re_string = re_string + key + " "
+    end
+  end
+  return re_string
 end
 
 h = {
@@ -9,11 +17,9 @@ def find_max(hash)
   "b" => 38,
   "c" => 21,
   "d" => 80,
-  "e" => 10
+  "e" => 80
 }
 
 answer = find_max(h)
 
 puts "有最大 value 的是 #{answer}" # 应该是 d
-
-
diff --git a/24-hash-even.rb b/24-hash-even.rb
index 9da9605..4c704c9 100644
--- a/24-hash-even.rb
+++ b/24-hash-even.rb
@@ -1,9 +1,13 @@
 # 给定一 Hash，输出 value 是偶数的 keys
 
 def find_even_keys(hash)
-
-  # ... (请回传一个数组)
-
+  even_key = []
+  hash.each do |key, value|
+    if value % 2 == 0
+      even_key.push(key)
+    end
+  end
+  return even_key
 end
 
 h = {
@@ -17,5 +21,3 @@ def find_even_keys(hash)
 answer = find_even_keys(h)
 
 puts "有偶数 value 的 keys 有 #{answer}" # 应该是数组 [b,d,e]
-
-
diff --git a/25-hash-count.rb b/25-hash-count.rb
index 2167335..af3045f 100644
--- a/25-hash-count.rb
+++ b/25-hash-count.rb
@@ -3,8 +3,32 @@
 def count(arr)
   h = {}
 
+  #相当于 uniq
+  # count = []
+  # arr.each do |i|
+  #   if count.include?("i")
+  #   else
+  #     count << i
+  #   end
+  # end
+  #
+  # count.each do |i|
+  #   h[i] = arr.count(i)
+  # end
+
+
+  # arru = arr.uniq
+  # arru.each do |i|
+  #   h[i] = arr.count(i)
+  # end
+
+  # 另外一种高效的写法
   arr.each do |i|
-    # ...
+    if h[i] == nil
+      h[i] = 1
+    else
+      h[i] = h[i] + 1
+    end
   end
 
   return h # 回传一个 hash
@@ -15,4 +39,3 @@ def count(arr)
 answer = count(arr)
 
 puts answer # 答案应该是 {"a"=>3, "d"=>6, "c"=>5, "b"=>1, "e"=>5}
-
diff --git a/26-hash-filter.rb b/26-hash-filter.rb
index 51ade64..ff2baa0 100644
--- a/26-hash-filter.rb
+++ b/26-hash-filter.rb
@@ -8,9 +8,19 @@
   { "name" => "Vincent", "age" => 6 },
 ]
 
-# ....
+# 找出成年人，生成新的数组
+adult = []
+arr.each do |i|
+  if i["age"] > 18
+    adult << i
+  end
+end
 
-puts "所有成年人，并由小到大: _________"
+# 排序
+result = adult.sort_by{|i| i["age"] }
+
+
+puts "所有成年人，并由小到大:#{result}"
 
 # 答案应该是
 #[
diff --git a/27-class.rb b/27-class.rb
index 8cec2c9..efa46d2 100644
--- a/27-class.rb
+++ b/27-class.rb
@@ -1,16 +1,27 @@
 class Person
-  # ...
-end
-
-p1 = Person.new
-p1.first_name = "Peter"
-p1.last_name = "Wang"
-p1.greet # 输出 "Hello, Peter Wang"
+  attr_accessor :first_name, :last_name
 
-p2 = Person.new
-p2.first_name = "William"
-p2.last_name = "Zhang"
-p2.greet # 输出 "Hello, William Zhang"
+  def initialize(first, last)
+     @first_name = first
+     @last_name  = last
+  end
 
+  def greet
+    puts "Hello, #{first_name} #{last_name}"
+  end
+end
 
+# p1 = Person.new
+# p1.first_name = "Peter"
+# p1.last_name = "Wang"
+# p1.greet # 输出 "Hello, Peter Wang"
+#
+# p2 = Person.new
+# p2.first_name = "William"
+# p2.last_name = "Zhang"
+# p2.greet # 输出 "Hello, William Zhang"
 
+p3 = Person.new("王", "明")
+p3.first_name
+p3.last_name
+p3.greet
diff --git a/28-word-count.rb b/28-word-count.rb
index 2643123..dbd936e 100644
--- a/28-word-count.rb
+++ b/28-word-count.rb
@@ -2,4 +2,18 @@
 
 doc = File.read("wordcount.txt")
 
-# ...
+h = {}
+
+doc.each_line { |line|
+  words = line.split
+  words.each { |w|
+    word = w.gsub(/[,()'".]/, '').downcase
+    if h.has_key?(word)
+      h[word] = h[word] + 1
+    else
+      h[word] = 1
+    end
+  }
+}
+
+puts h
diff --git a/29-todos.rb b/29-todos.rb
index 0bddde2..caec58b 100644
--- a/29-todos.rb
+++ b/29-todos.rb
@@ -2,6 +2,7 @@
 
 text = File.read("todos.txt")
 
+
 todos = []
 text.each_line do |line|
   todos << line.chomp
@@ -11,23 +12,29 @@
   puts "#{index}: #{todo}"
 end
 
+
 while (true)
   print "请输入指令 1. add 2. remove 3. save，然后按 Enter: "
   command = gets.chomp
 
   if command == "add"
     print "请输入代办事项: "
-    # ...
+    new_event = gets.chomp
+    todos << new_event
   elsif command == "remove"
     print "请输入要删除的编号: "
-    # ...
+    code = gets.chomp.to_i
+    todos.delete_at(code)
   elsif command == "save"
     puts "存盘离开"
-
-    # ...
+    File.open("todos.txt", "w+") do |f|
+      todos.each do |line|
+        f << line
+        f << "\n"
+      end
+    end
     break;
   else
     puts "看不懂，请再输入一次"
   end
 end
-
diff --git a/arithmetic/01-bucket.rb b/arithmetic/01-bucket.rb
new file mode 100644
index 0000000..00e3b2e
--- /dev/null
+++ b/arithmetic/01-bucket.rb
@@ -0,0 +1,37 @@
+a = []
+for i in 0..10 do
+  a[i] = 0
+end
+print a
+
+puts "\n"
+a[2] = 1
+a[3] = 1
+a[5] = 2
+a[8] = 1
+
+# 正序排列
+for i in 0..10 do
+  j = 1
+  while j <= a[i]
+    print i
+    j += 1
+  end
+end
+
+puts "\n"
+# 反序排列
+i = 10
+while i >=0
+  j = 1
+  while j <= a[i]
+    print i
+    j += 1
+  end
+  i -= 1
+end
+puts "\n"
+# 结果是：
+# [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
+# 23558
+# 85532
diff --git a/arithmetic/02-popo.rb b/arithmetic/02-popo.rb
new file mode 100644
index 0000000..055c656
--- /dev/null
+++ b/arithmetic/02-popo.rb
@@ -0,0 +1,33 @@
+# 实践冒泡排序
+
+def selection_sort(arr)
+  i = 0                   # 用来计算外循环次数 ，参与内循环次数计算
+  temp = []               # 用于冒泡的数据交换
+  while i < arr.size - 1  # 只比较n-1次，因为有n个数
+    j = 1                 # 初始化内循环的key。
+
+    while j < arr.size - i
+      # 每次循环内循环结束后，把最大／小值放到数组最后，
+      # 下一次外循环的内循环，就不比较已经定位的数字了，用每次外循环初始化j = 1来实现。所以每次外循环都会减少一次内循环，用减 i 来实现。
+      # 第一次外循环时，内循环比较9次；第二次外循环时，内循环比较8次；依次递减至结束。
+      if arr[j-1] <= arr[j]  #如果true则交换值
+      # 大于等于 是 从小到大排序
+      # 小于等于 是 从大到小排序
+        temp = arr[j -1]
+        arr[j-1] = arr[j]
+        arr[j] = temp
+      end
+      j = j + 1
+    end
+
+    i = i + 1
+  end
+
+  return arr
+end
+
+arr =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
+
+answer = selection_sort(arr)
+
+puts answer.to_s
diff --git a/arithmetic/03-binary.rb b/arithmetic/03-binary.rb
new file mode 100644
index 0000000..6f6696a
--- /dev/null
+++ b/arithmetic/03-binary.rb
@@ -0,0 +1,37 @@
+
+def quicksort(a,left,right)
+  if left > right            # 设定何时停止该方法的调用。
+    return
+  end
+
+  temp = a[left]              #设定最左边的为基准数
+  i = left
+  j= right
+  while i != j                   # i和j从两边向中间靠拢，直到i和j重合，结束本轮循环。
+    while a[j] <= temp && i < j  #顺序很重要，要先从右往左找。找大于基准数的数，则降序排序。
+      j -= 1
+    end
+    while a[i] >= temp && i < j  #再向➡️找,根据是升序还是降序来选择 比较运算符号，此例找小于基准数的数。
+      i += 1
+    end
+    if i < j                    #当i 和 j 没有相遇的时候，交换数据
+      t = a[i]
+      a[i] = a[j]
+      a[j] = t
+    end
+  end
+  a[left] = a[i]              #将基准数归位。
+  a[i] = temp
+  print a.to_s + "\n"
+  quicksort(a,left,i-1)       # 在quciksort的方法中，再次调用本方法，形成递归的过程。这个是处理i左边。直到穷尽，即当left>right时停止调用该方法。
+  quicksort(a,i+1,right)      # 这个处理i右边
+  
+end
+
+
+
+a =  [7, 68, 42, 46, 9, 91, 77, 46, 86, 1]
+
+quicksort(a,0,9)
+# 0和9 代表数组最左边和最右边的key
+print a
diff --git a/todos.txt b/todos.txt
index 4757e85..a0057b6 100644
--- a/todos.txt
+++ b/todos.txt
@@ -1,4 +1 @@
-Buy book
-Go Shopping
-Walk
-Gogo
+work2