关于排序——ruby版练手

冒泡&选择排序

快排两种写法，第一种用ruby的partition，简短，第二种为常规快排写法

arr1 = [4, 6, 2, 7, 1, 3, 8, 9, 5, 0]arr2 = [8, 12, 4, 14, 2, 6, 16, 18, 10, 20]arr3 = [8, 12, 4, 14, 2, 6, 16, 18, 10, 20]arr4 = [8, 12, 4, 14, 2, 6, 16, 18, 10, 20]#冒泡——两两比较，发现两元素的次序相反时即交换def bubble_sort(arr)  0.upto(arr.length - 1) do |i|    1.upto(arr.length - 1 - i) do |j|         if ( arr[j-1] > arr[j] )           tmp = arr[j-1]           arr[j-1] = arr[j]           arr[j] = tmp         end    end  endendbubble_sort(arr1)p arr1#选择排序——每次从待排数据汇总选出最值，放在已拍好的序列最后def selection_sort(arr)  0.upto(arr.length - 2) do |i|      (i+1).upto(arr.length - 1) do |j|        if(arr[i] > arr[j])          tmp = arr[i]          arr[i] = arr[j]          arr[j] = tmp        end      end  endendinsert_sort(arr2)p arr2#快排——ruby方法partition ——选择一基准元素，划分左右两个无序区间，该基准元素放在其最终位置上，再不断递归快排左右两序列，最坏O(n^2)，平均O(nlogn）def qsort(arr) return arr if arr.length == 0  mid = arr[0]  a = arr[1...arr.length]#  mid, a[] = arr  small, big = a.partition do |tmp|    tmp < mid  end  return qsort(small) + [mid] + qsort(big)endp qsort(arr3)#快排def qsort2(arr, lef, rig)  return if lef >= rig  i = lef  j = rig  mid = arr[lef]  pos = lef  while (i < j)    while( i < j && arr[j] >= mid)      j = j - 1    end    while( i < j && arr[i] <= mid)      i = i+1    end    if (i <= j)      arr[pos] = arr[j]      arr[j] = arr[i]      arr[i] = mid      pos = i    end  end  qsort2(arr, lef, pos - 1)  qsort2(arr, pos + 1, rig)endp arr4qsort2(arr4, 0, arr4.length - 1)p arr4