| A | B | C | D | E | |
| 1 | =file("Article.btx") | =create(Word,Count,Index) |
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| 2 | =A1.cursor@b() |
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| 3 | for A2 | =A3.Text | =len(B3) |
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| 4 | =C3.(mid(B3,#,1)) | =B4.(if(isalpha(~),lower(~)," ")) |
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| 5 | =C4.select(~!=" "||~[-1]!=" ") | =B5.concat().split(" ") |
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| 6 | =C5.groups(string(~):Word;count(~):Count) | =B6.len() |
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| 7 | =B1.len() | >i1=min(1,B7) | >i2=1 |
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| 8 | for i2<=C6 | =B1.m(i1) | =B6(i2) |
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| 9 | =cmp(C8.Word,D8.Word) |
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| 10 | if i1==0||C9>0 | >B1.insert(i1,D8.Word,D8.Count,[#A3]) |
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| 11 | =i2=i2+1 | ||||
| 12 | >i1=if(i1>0 && i1<B7,i1+1,0) | ||||
| 13 | else if C9<0 | >i1=if(i1>0 && i1<B7,i1+1,0) |
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| 14 | else | >B1.modify(i1,Count+D8.Count:Count,Index|#A3:Index) |
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| 15 | >i2=i2+1 | ||||
| 16 | >i1=if(i1>0&&i1<B7,i1+1,0) | ||||
| 17 | =file("Article_index.btx") | >A17.export@b(B1) |
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问题中未限定内存，一般情况下，英语单词的数量是有限的，因此在计算汇总时，直接用序表存储索引表。有了二进制索引文件Article_index，我们就可以根据一个或多个关键词，找出相关文本：
| A | B | C | D | |
| 1 | =file("Article.btx") | =file("Article_index.btx") |
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| 2 | =B1.import@b() | [about,will] |
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| 3 | =A2.(Word).pos(B2) | =A2(A3).(Index).isect() |
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| 4 | =A1.cursor@b() | [] | 0 |
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| 5 | for B3 | >A4.skip(A5-C4-1) | >C4=A5 |
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| 6 | >B4=B4|A4.fetch(1) |
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| 7 | >A4.close() |
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整理完的索引序表如下：
最终的查找结果如下：
