分段线性插值的C++代码实现，实现了基本的插值功能和方程拟合，可供初学者使用-Piecewise linear interpolation C++ code to achieve the basic functions and interpolation equation fitted for beginners to use

掌握用MATLAB计算拉格朗日,分段线性,三次样条三种插值的方法(Master the MATLAB computing Lagrange, piecewise linear, three kinds of cubic spline interpolation method)