[POJ3678] Katu Puzzle | 2-SAT 入门
Description Katu Puzzle is presented as a directed graph G ( V , E ) with each edge e ( a , b ) labeled by a boolean operator op (oneofAND,OR,XOR) and an integer c ( 0 ≤ c ≤ 1 ) . One Katu is solvable if one can find each vertex Vi a value X i ( 0 ≤ X i ≤ 1 )