Inverted index

程序设计

倒排索引（inverted index）也称为反向索引。

Example

From sentences

T_0 = "it is what it is"
T_1 = "what is it"
T_2 = "it is a banana"

We can form inverted indexes:

 "a":      {2}
 "banana": {2}
 "is":     {0, 1, 2}
 "it":     {0, 1, 2}
 "what":   {0, 1}

Searching for ('what', 'is', 'it') obtains $\{0,1\} \cap \{0,1,2\} \cap \{0,1,2\} = \{0,1\}$.