用Erlang实现二分查找算法

算法实现如下

 1 -module(bisearch).
 2 -export([start/2]).
 3 
 4 start(Value,List) ->
 5     Len = length(List),
 6     FirstValue = lists:nth(1, List),
 7     LastValue = lists:nth(Len, List),
 8     if FirstValue =:= Value orelse LastValue =:= Value ->
 9             io:format("found ~w~n", [Value]);  % 查找值在列表的首尾
10         true ->
11             Result = calu(1, length(List), Value, List),
12             case Result of
13                 found -> io:format("found ~w~n", [Value]);
14                 _ -> io:format("not found ~w~n", [Value])
15             end
16     end.
17 
18 %% 二分查找
19 calu(L, H, Value, List) ->
20     M = (L+H) div 2,
21     case L =:= M of
22         true -> none;  % 查找范围段只有两个元素，结束查找
23         false ->
24             MValue = lists:nth(M, List), % 计算中值
25             if
26                 Value =:= MValue ->
27                     found;               % 查找成功
28                 Value < MValue ->
29                     calu(L, M, Value, List); % 设置列表的前段为新的查找范围
30                 Value > MValue ->
31                     calu(M, H, Value, List)  % 设置列表的后段为新的查找范围
32             end
33     end.

 

posted on 2012-12-13 16:29  应无所住而生其心  阅读(525)  评论(0)  编辑  收藏  举报

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