feat: Add Ruby code - chapter "computational complexity" (#1212)

* feat: add ruby code - chapter computational complexity

* feat: add ruby code blocks

codes/ruby/chapter_computational_complexity/iteration.rb

@@ -0,0 +1,78 @@
+=begin
+File: iteration.rb
+Created Time: 2024-03-30
+Author: Xuan Khoa Tu Nguyen (ngxktuzkai2000@gmail.com)
+=end
+
+### for 循环 ###
+def for_loop(n)
+  res = 0
+
+  # 循环求和 1, 2, ..., n-1, n
+  for i in 1..n
+    res += i
+  end
+
+  res
+end
+
+### while 循环 ###
+def while_loop(n)
+  res = 0
+  i = 1 # 初始化条件变量
+
+  # 循环求和 1, 2, ..., n-1, n
+  while i <= n
+    res += i
+    i += 1 # 更新条件变量
+  end
+
+  res
+end
+
+### while 循环（两次更新）###
+def while_loop_ii(n)
+  res = 0
+  i = 1 # 初始化条件变量
+
+  # 循环求和 1, 4, 10, ...
+  while i <= n
+    res += i
+    # 更新条件变量
+    i += 1
+    i *= 2
+  end
+
+  res
+end
+
+### 双层 for 循环 ###
+def nested_for_loop(n)
+  res = ""
+
+  # 循环 i = 1, 2, ..., n-1, n
+  for i in 1..n
+    # 循环 j = 1, 2, ..., n-1, n
+    for j in 1..n
+      res += "(#{i}, #{j}), "
+    end
+  end
+
+  res
+end
+
+### Driver Code ###
+
+n = 5
+
+res = for_loop n
+puts "\nfor 循环的求和结果 res = #{res}"
+
+res = while_loop n
+puts "\nwhile 循环的求和结果 res = #{res}"
+
+res = while_loop_ii n
+puts "\nwhile 循环（两次更新）求和结果 res = #{res}"
+
+res = nested_for_loop n
+puts "\n双层 for 循环的遍历结果 #{res}"