基于VC的三种端点条件的插值B样条曲线绘制，包括夹持端点，自由端点，抛物线端点，线性方程组的解法采用了追赶法。-VC based on the conditions of the three endpoint interpolation B-spline curve drawing, including the gripping end, the Liberal endpoint, the endpoint parabola, the solution of linear equations u