Luke's Sort Exercises

README.md

@@ -1,2 +1,4 @@
 # assignment_sort
 Insertion and Merge Sort assignment
+
+Completed by John Popenuck, Jessica Gillan and Luke Schleicher

warmups.rb

@@ -0,0 +1,108 @@
+def insertion_sort(arr)
+  return arr if arr.length <= 1
+
+  for element in 1...arr.length
+
+    value = arr[element]
+    end_of_sorted_list = element - 1
+
+    while(end_of_sorted_list >= 0 && arr[end_of_sorted_list] > value)
+        arr[end_of_sorted_list + 1] = arr[end_of_sorted_list]
+        end_of_sorted_list -= 1
+    end
+
+    arr[end_of_sorted_list + 1] = value
+
+  end
+
+  arr
+
+end
+
+# array = [8, 2, -5, 0, 9, -11]
+# print insertion_sort(array)
+
+def bubble_sort(arr)
+  return arr if arr.length <= 1
+
+  swap = true
+  end_of_unsorted_list = arr.length - 1
+
+  while swap
+    swap = false
+    (0..end_of_unsorted_list - 1).each do |left_item|
+      right_item = left_item + 1
+      if arr[left_item] > arr[right_item]
+        arr[left_item], arr[right_item] = arr[right_item], arr[left_item]
+        swap = true
+      end
+    end
+    end_of_unsorted_list -= 1
+  end
+  arr
+end
+
+# array = [8, 2, -5, 0, 9, -11]
+# print bubble_sort(array)
+
+# MERGE SORT = RECURSIVE DIVIDE AND CONQUER
+# recursively divide initial array in to two parts until have arrays of one item
+# split each item in to its own section
+
+# keep going to combine all back in to large array
+# Recursive divide and conquer
+def merge_sort(unsorted_arr)
+  return unsorted_arr if unsorted_arr.length <= 1
+
+  left = merge_sort( unsorted_arr[0..(unsorted_arr.length/2 - 1) ] )
+  right = merge_sort( unsorted_arr[(unsorted_arr.length/2)..-1])
+  merge(left, right)
+end
+
+# Merge the returns of recursive calls to merge sort
+
+#  MERGE TWO SORTED ARRAYS - RETURN A SORTED ARRAY
+    # compare item 0 to item 1, swap so ascending order
+    # move to items 2,3 4,5 6,7  iteration
+    # once each pair is sorted, combine in to 2 element array
+    # then combine pair arrays by  ...
+    # look at first value in each
+    # put smaller one in new array, pop off old pair array
+    # look at first item in each again
+    # unless one of the arrays is emtpy, then push remaining array on to new array
+    # in entirety
+def merge(left, right)
+  return_array = []
+  # think about splitting lines 78 - 83 out after until loop
+  until left.empty? && right.empty?
+    if left.empty?
+      return_array += right
+      right = []
+    elsif right.empty?
+      return_array += left
+      left = []
+    else
+      if left[0] >= right[0]
+        return_array.push right.shift
+      else
+        return_array.push left.shift
+      end
+    end
+  end
+  return_array
+end
+# refactor so it doesn't utilize shift and uses indexes instead
+
+def benchmark(arr)
+  start = Time.now
+  100.times { insertion_sort(arr) }
+  puts "insertion time = #{Time.now - start}"
+  start = Time.now
+  100.times { bubble_sort(arr) }
+  puts "bubble time = #{Time.now - start}"
+  start = Time.now
+  100.times { merge_sort(arr) }
+  puts "merge time = #{Time.now - start}"
+end
+array = Array.new(8027){rand(0..14525653645)}
+benchmark(array)