COMPUTER PRODUCT, INFORMATION RETRIEVAL METHOD, AND INFORMATION RETRIEVAL APPARATUS

A computer-readable recording medium stores therein an information retrieval program that causes a computer to execute a retrieval process in which files to be retrieved are narrowed down by using a bit string for each character in the files to find characters making up a retrieval keyword to retrieve a keyword identical to or related to the retrieval keyword in the files to be retrieved. The bit strings indicate the presence of the characters in the files. The information retrieval program causes the computer to execute extracting, from among the bit strings, a bit string of an arbitrary character; and compressing the extracted bit string, by using a special Huffman tree having leaves of plural types of symbol strings covering patterns represented by a predetermined number of bits and a special symbol string having a number of bits greater than the predetermined number of bits.