计算机科学 ›› 2026, Vol. 53 ›› Issue (5): 346-353.doi: 10.11896/jsjkx.250800047
王永平1, 符祖峰2
WANG Yongping1, FU Zufeng2
摘要: 严格d-正则(3,s)-SAT问题是指:给定一个严格d-正则(3,s)-CNF公式,判定是否存在对其变量的一个真值指派,使公式的真值为真。此处,严格d-正则(3,s)-CNF公式是指:每个子句的长度为3,每个变量的出现次数为s,每个变量的正、负出现次数之差的绝对值为d 的CNF公式。研究表明,一定条件下,严格d-正则(3,s)-SAT问题存在难解实例聚集现象。因此,讨论了严格d-正则(3,s)-SAT问题的计算复杂性,证明了:当 s≥4 时,存在不可满足的严格(s-2)-正则(3,s)-CNF公式和不可满足的严格(s-4)-正则(3,s)-CNF公式。由此,已有的系列结论中的假设条件成为现实。于是,严格d-正则(3,s)-SAT问题的计算复杂性得以解决:当 s≤3 时,严格d-正则(3,s)-CNF公式均可满足;当s≥4 且d<s时,严格d-正则(3,s)-SAT问题是NP-完全问题;当 s≥4 且d=s时,严格d-正则(3,s)-CNF公式均可满足。需指出,所得结论意味着,严格0-正则(3,4)-SAT问题和严格2-正则(3,4)-SAT问题均是NP-完全问题,即严格0-正则(3,4)-SAT问题和严格2-正则(3,4)-SAT问题保留了正则(3,4)-SAT问题的NP-完全性,也保留了3-SAT问题的NP-完全性。因此,继续研究严格d-正则(3,s)-SAT问题,尤其是严格0-正则(3,4)-SAT问题和严格2-正则(3,4)-SAT问题应该是必要的。
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