Re: [理工] [離散]-成大99
原題照我印象應該是..
女男配對問題
四女 五男
女1不配男1,3,5
女2不配男2,4
女3不配男1,3
女4不配男4
利用排容
__ __ __ __
令Ai表示女i與其不願意男配對 求N(A1 A2 A3 A4)
__ __ __ __
N(A1 A2 A3 A4) = S0 - S1 + S2 - S3 + S4
S0 = 5! = 120
S1 = N(A1) + N(A2) + N(A3) + N(A4)
= 4!( 3 + 2 + 2 + 1 )
= 192
S2 = N(A1 A2) + N(A1 A3) + N(A1 A4) + N(A2 A3) + N(A2 A4) + N(A3 A4)
= 3!( 3x2 + 2+2 + 3 + 2x2 + 1 + 2 )
= 120
S3 = N(A1 A2 A3) + N(A1 A2 A4) + N(A1 A3 A4) + N(A2 A3 A4)
= 2!( 2x(2+2) + 3 + 2+2 + 2 )
= 34
S4 = N(A1 A2 A3 A4)
= 1!(2+2)
= 4
__ __ __ __
N(A1 A2 A3 A4) = 120 - 192 + 120 - 34 + 4 = 18
在考場寫這題花了快三十分鐘 ... 結果S0寫成5^4.... 噢死 = ="
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