复旦大学：《离散数学》PPT教学课件（赵一鸣）22/28

o(1)a(2)…(m) 12 (1)a(2)…o(n)(a(1)o(i2)…a(n)

        = (1) (2) ( ) 1 2 n n               =        = (1) (2) ( ) ( ) ( ) ( ) 1 2 1 2 1 2 n n i i i i i i n n           

identity permutation e a(1)a(2)…a(n) inverse permutation of o o 2 a1(1)a(2)…a(n)

        =         =         = − − − − − σ (1) σ (2) σ (n) 1 2 n σ 1 2 n σ(1) σ(2) σ(n) σ 1 2 n 1 2 n e 1 1 1 1 1       inverse permutation of  identity permutation