Patent ID: 8453249

Claim:
A document checking apparatus comprising: a memory; and a processor coupled to the memory, wherein the processor executes a process comprising: extracting keywords from a target document and a confidential document that becomes a comparison target when determining similarity between documents; first determining, based on appearance positions of the keywords extracted at the extracting whether another keyword is within a predetermined range extending from a target keyword toward either front or rear of the documents, to determine an element of feature element information corresponding to a pair of the target keyword and the another keyword within the predetermined range; generating, when it is determined at the first determining that there is the another keyword, the feature element information having a specific value in the element determined at the first determining; comparing the feature element information of the target document and the feature element information of the confidential document generated at the generating; and second determining whether a number of common elements having the specific value commonly among the feature element information of the target document and the confidential document is not less than a first similarity determination number to determine similarity between the target document and the confidential document on the basis of the determination result, generating, as the feature element information, a feature element matrix having the specific value in a matrix element determined at the first determining, generating matrix information that is obtained setting to a specific value matrix elements obtained by combining hash values of the determination target keywords and a hash value of the another keyword in association with row information and column information as a plurality of combination information, generating common matrix information that is obtained by setting a specific value matrix elements corresponding to the same matrix elements having the specific value of both matrix information of the determination target document and a specific document, and extracting row information having a plurality of specific values for each the same column information from the common matrix information and determining whether a number of matrix elements that are obtained by combining two different row information among the extracted row information and have the specific value is not less than the second similarity determination number.