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[题目来源]：tyvj1128

[关键字]：字典树

[题目大意]：给出一个字典。接着输入字符串s查询最多前8个依次为前缀的字典中的单词，如没有只输出s。

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[分析]：用字典树，首先将每个单词插入字典树，然后寻找到s插入字典树后在字典树中的节点，以此为起点进行dfs，如果s无法插入树中说明没有依次为前缀得单词。

[代码]：

View Code

 1 program Project1;
 2 type
 3   rec = record
 4     dat: array['a'..'z'] of longint;
 5     f: boolean;
 6     s: string;
 7   end;
 8 var
 9   tot, tn, n, q: longint;
10   tree: array[0..2000000] of rec;
11 
12 procedure inser(s: string);
13 var
14   i, now: longint;
15 begin
16   now := 1;
17   for i := 1 to length(s) do
18     if tree[now].dat[s[i]] <> 0 then now := tree[now].dat[s[i]]
19     else
20       begin
21         inc(tn);
22         tree[tn].f := false;
23         tree[now].dat[s[i]] := tn;
24         now := tn;
25       end;
26   tree[now].s := s;
27   tree[now].f := true;
28 end;
29 
30 procedure dfs(k: longint);
31 var
32   ch: char;
33 begin
34   if tree[k].f then
35     begin
36       inc(tot);
37       write(tree[k].s,'');
38     end;
39   for ch := 'a' to 'z' do
40     begin
41       if tree[k].dat[ch] <> 0 then dfs(tree[k].dat[ch]);
42       if tot = 8 then exit;
43     end;
44 end;
45 
46 procedure find(s: string);
47 var
48   now, i: longint;
49 begin
50   now := 1;
51   for i := 1 to length(s) do
52     if tree[now].dat[s[i]] <> 0 then now := tree[now].dat[s[i]]
53     else exit;
54   dfs(now);
55 end;
56 
57 procedure init;
58 var
59   i: longint;
60   s: string;
61 begin
62   readln(n);
63   tn := 1;
64   for i := 1 to n do
65     begin
66       readln(s);
67       inser(s);
68     end;
69   readln(q);
70   for i := 1 to q do
71     begin
72       readln(s);
73       tot := 0;
74       find(s);
75       if tot = 0 then writeln(s) else writeln;
76     end;
77 end;
78 
79 begin
80   //assign(input,'c:\1.in');reset(input);
81   assign(output,'c:\1.out');rewrite(output);
82   init;
83   close(input);
84   close(output);
85 end.