finish exercise

README.md

@@ -1,2 +1,4 @@
 # assignment_sort
 Insertion and Merge Sort assignment
+
+Tingting Wang

bubble.rb

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+require 'pry'
+
+def bubble_sort(array)
+  last = array.length - 2
+
+  array.length.times do
+    (0..last).each do |index|
+      first = array[index]
+      second = array[index+1] 
+      if first > second 
+        array[index], array[index+1] = second, first
+      end
+    end
+  end
+  array
+end

insertion.rb

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+def insert(array, right_index, value)
+    # value is the value of array[right_index + 1]
+    # right_index is the furthest right sorted element
+
+    # Step through sorted elements right to left.
+    # As long as your value is less than the element
+    # at array[i] and you still have elements
+    i = right_index
+    while(i >= 0 && array[i] > value)
+        # copy the element
+        array[i+1] = array[i]
+        i -= 1
+    end
+
+    # insert the actual element
+    array[i+1] = value;
+end
+
+def insertion_sort(array)
+    array.each_with_index do |value, index|
+        right_index = index-1
+        insert(array, right_index, value)
+    end
+    array
+end

merge.rb

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+def merge_sort(array)
+  return array if array.length <= 1 
+
+  split = array.length / 2
+  left = array[0..split-1]
+  right = array[split..-1]
+
+  left_merge = merge_sort(left)
+  right_merge = merge_sort(right)
+
+  merge(left_merge, right_merge)
+
+end
+
+def merge(left_merge, right_merge)
+  sorted = []
+  until left_merge.empty? && right_merge.empty?
+    if left_merge.empty?
+      sorted += right_merge
+      right_merge = []
+    elsif right_merge.empty?
+      sorted += left_merge
+      left_merge = []
+    elsif left_merge[0] <= right_merge[0]
+      sorted << left_merge.shift
+    elsif right_merge[0] < left_merge[0]
+      sorted << right_merge.shift
+    end
+  end
+  sorted
+end