邮件服务器技术概述
2007-12-08 11:00
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原code参见http://en.literateprograms.org/Bubble_sort_(Erlang)
虽然原文有解释,可能还是不太好理解erlang写得这么间断晦涩的程序。
我们先看一个例子吧:
sort([2,4,3,5,1])
#round 1
=> sort([2,4,3,5,1], [], true)
=> sort([4,3,5,1], [2], true)
=> sort([4,5,1], [3,2], false)
=> sort([5,1], [4,3,2], false)
=> sort([5], [1,4,3,2], false)
=> sort([], [5,1,4,3,2], false)
=> sort([2,3,4,1,5], [], true)
# round 2
=> sort([3,4,1,5], [2], true)
=> sort([4,1,5], [3,2], true)
=> sort([4,5], [1,3,2], false)
=> sort([5], [4,1,3,2], false)
=> sort([], [5,4,1,3,2], false)
=> sort([2,3,1,4,5], [], true)
# round 3
=> sort([3,1,4,5], [2], true)
=> sort([3,4,5], [1,2], false)
=> sort([4,5], [3,1,2], false)
=> sort([5], [4,3,1,2], false)
=> sort([], [5,4,3,1,2], false)
=> sort([2,1,3,4,5], true)
#round 4
=> sort([2,3,4,5], [1], false)
=> sort([3,4,5], [2,1], false)
=> sort([4,5], [3,2,1], false)
=> sort([5], [4,3,2,1], false)
=> sort([], [5,4,3,2,1], false)
=> sort([1,2,3,4,5], [], true)
#round 5
=> sort([2,3,4,5], [1], true)
=> sort([3,4,5],[2,1], true)
=> sort([4,5],[3,2,1], true)
=> sort([5],[4,3,2,1], true)
=> sort([], [5,4,3,2,1], true)
=> [1,2,3,4,5]
冒泡排序的每一轮,都找出了一个最大值沉到队伍的最后面.如果本轮全部是排好序的,也即不需要下一轮了,那么flag就是true,否则是false.
虽然原文有解释,可能还是不太好理解erlang写得这么间断晦涩的程序。
1 % Copyright (c) 2012 the authors listed at the following URL, and/or 2 % the authors of referenced articles or incorporated external code: 3 % http://en.literateprograms.org/Bubble_sort_(Erlang)?action=history&offset=20080418062156 4 % 5 % Permission is hereby granted, free of charge, to any person obtaining 6 % a copy of this software and associated documentation files (the 7 % "Software"), to deal in the Software without restriction, including 8 % without limitation the rights to use, copy, modify, merge, publish, 9 % distribute, sublicense, and/or sell copies of the Software, and to 10 % permit persons to whom the Software is furnished to do so, subject to 11 % the following conditions: 12 % 13 % The above copyright notice and this permission notice shall be 14 % included in all copies or substantial portions of the Software. 15 % 16 % THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 17 % EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 18 % MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 19 % IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 20 % CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, 21 % TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE 22 % SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. 23 % 24 % Retrieved from: http://en.literateprograms.org/Bubble_sort_(Erlang)?oldid=13141 25 26 -module(bubblesort). 27 -export([sort/1]). 28 -import(lists, [reverse/1]). 29 30 sort(L) -> sort(L, [], true). 31 32 sort([], L, true) -> reverse(L); 33 34 sort([], L, false) -> sort(reverse(L), [], true); 35 sort([ X, Y | T ], L, _) when X > Y -> 36 sort([ X | T ], [ Y | L ], false); 37 sort([ X | T ], L, Halt) -> sort(T, [ X | L ], Halt).
我们先看一个例子吧:
sort([2,4,3,5,1])
#round 1
=> sort([2,4,3,5,1], [], true)
=> sort([4,3,5,1], [2], true)
=> sort([4,5,1], [3,2], false)
=> sort([5,1], [4,3,2], false)
=> sort([5], [1,4,3,2], false)
=> sort([], [5,1,4,3,2], false)
=> sort([2,3,4,1,5], [], true)
# round 2
=> sort([3,4,1,5], [2], true)
=> sort([4,1,5], [3,2], true)
=> sort([4,5], [1,3,2], false)
=> sort([5], [4,1,3,2], false)
=> sort([], [5,4,1,3,2], false)
=> sort([2,3,1,4,5], [], true)
# round 3
=> sort([3,1,4,5], [2], true)
=> sort([3,4,5], [1,2], false)
=> sort([4,5], [3,1,2], false)
=> sort([5], [4,3,1,2], false)
=> sort([], [5,4,3,1,2], false)
=> sort([2,1,3,4,5], true)
#round 4
=> sort([2,3,4,5], [1], false)
=> sort([3,4,5], [2,1], false)
=> sort([4,5], [3,2,1], false)
=> sort([5], [4,3,2,1], false)
=> sort([], [5,4,3,2,1], false)
=> sort([1,2,3,4,5], [], true)
#round 5
=> sort([2,3,4,5], [1], true)
=> sort([3,4,5],[2,1], true)
=> sort([4,5],[3,2,1], true)
=> sort([5],[4,3,2,1], true)
=> sort([], [5,4,3,2,1], true)
=> [1,2,3,4,5]
冒泡排序的每一轮,都找出了一个最大值沉到队伍的最后面.如果本轮全部是排好序的,也即不需要下一轮了,那么flag就是true,否则是false.
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