拉格朗日插值算法，输入[x0 x1 x2]和对应的[y0 y1 y2]，按拉格朗日插值发计算出[x0 x2]之间任何一个X所对应的Y值-Lagrange interpolation algorithm, type [x0 x1 x2] and the corresponding [y0 y1 y2], issued by the Lagrange interpolation to calculate [x0 x2] between any one of X corresponding to Y