思路:矩阵A.M[i][j]代表第i个人在第j个位置的方案数。 Ai.M[i][1] = Ai-1.M[i][1] + Ai-1.M[i][2] + Ai-1.M[i][4] Ai.M[i][2] = Ai-1.M[i][1] + Ai-1.M[i][2] + Ai-1.M[i][3] Ai.M[i][3] = Ai-1.M[i][2] + Ai-1.M[i][3] + Ai-1.M[i][4] Ai.M[i][4] = Ai-1.M[i][1] + Ai-1.M[i][3] + Ai-1.M[i][4] 所以base矩阵为 ⎛⎝⎜⎜⎜110