高斯消元
用来求解方程组
a 11 x 1 + a 12 x 2 + ⋯ + a 1 n x n = b 1 a 21 x 1 + a 22 x 2 + ⋯ + a 2 n x n = b 2 … a n 1 x 1 + a n 2 x 2 + ⋯ + a n n x n = b n a_{11} x_1 + a_{12} x_2 + \dots + a_{1n} x_n = b_1\\ a_{21} x_1 + a_{22} x_2 + \dots + a_{2n} x_n = b_2\\ \dots \\ a_{n1} x_1 + a_{n2} x_2 + \dots + a_{nn} x_n = b_n\\ a11x1+a12x2+⋯+a1nxn=b1a21x1+a22x2+⋯+