We propose a novel algorithm based on random graphs to construct minimal perfect hash functions h. For a set of n keys, our algorithm outputs h in expected time O(n). The evaluation of h(x) requires two memory accesses for any key x and the description of h takes up 1.15n words. This improves the space requirement to 55% of a previous minimal perfect hashing scheme due to Czech, Havas and Majewski. A simple heuristic further reduces the space requirement to 0.93n words, at the expense of a slightly worse constant in the time complexity. Large scale experimental results are presented.
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